pimd: Fix memory leak in PIM interface deletion

pimd: Fix memory leak in PIM interface deletion

This commit ensures proper cleanup by deleting the gm_join_list when a PIM interface is deleted. The gm_join_list was previously not being freed, causing a memory leak.

The ASan leak log for reference:
```
***********************************************************************************
Address Sanitizer Error detected in multicast_mld_join_topo1.test_multicast_mld_local_join/r1.asan.pim6d.28070

=================================================================
==28070==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 40 byte(s) in 1 object(s) allocated from:
    #0 0x7f3605dbfd28 in __interceptor_calloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xded28)
    #1 0x56230373dd6b in qcalloc lib/memory.c:105
    #2 0x56230372180f in list_new lib/linklist.c:49
    #3 0x56230361b589 in pim_if_gm_join_add pimd/pim_iface.c:1313
    #4 0x562303642247 in lib_interface_gmp_address_family_static_group_create pimd/pim_nb_config.c:2868
    #5 0x562303767280 in nb_callback_create lib/northbound.c:1235
    #6 0x562303767280 in nb_callback_configuration lib/northbound.c:1579
    #7 0x562303768a1d in nb_transaction_process lib/northbound.c:1710
    #8 0x56230376904a in nb_candidate_commit_apply lib/northbound.c:1104
    #9 0x5623037692ba in nb_candidate_commit lib/northbound.c:1137
    #10 0x562303769dec in nb_cli_classic_commit lib/northbound_cli.c:49
    #11 0x56230376fb79 in nb_cli_pending_commit_check lib/northbound_cli.c:88
    #12 0x5623036c5bcb in cmd_execute_command_real lib/command.c:991
    #13 0x5623036c5f1b in cmd_execute_command lib/command.c:1053
    #14 0x5623036c6392 in cmd_execute lib/command.c:1221
    #15 0x5623037e75da in vty_command lib/vty.c:591
    #16 0x5623037e7a74 in vty_execute lib/vty.c:1354
    #17 0x5623037f0253 in vtysh_read lib/vty.c:2362
    #18 0x5623037db4e8 in event_call lib/event.c:1995
    #19 0x562303720f97 in frr_run lib/libfrr.c:1213
    #20 0x56230368615d in main pimd/pim6_main.c:184
    #21 0x7f360461bc86 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21c86)

Indirect leak of 192 byte(s) in 4 object(s) allocated from:
    #0 0x7f3605dbfd28 in __interceptor_calloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xded28)
    #1 0x56230373dd6b in qcalloc lib/memory.c:105
    #2 0x56230361b91d in gm_join_new pimd/pim_iface.c:1288
    #3 0x56230361b91d in pim_if_gm_join_add pimd/pim_iface.c:1326
    #4 0x562303642247 in lib_interface_gmp_address_family_static_group_create pimd/pim_nb_config.c:2868
    #5 0x562303767280 in nb_callback_create lib/northbound.c:1235
    #6 0x562303767280 in nb_callback_configuration lib/northbound.c:1579
    #7 0x562303768a1d in nb_transaction_process lib/northbound.c:1710
    #8 0x56230376904a in nb_candidate_commit_apply lib/northbound.c:1104
    #9 0x5623037692ba in nb_candidate_commit lib/northbound.c:1137
    #10 0x562303769dec in nb_cli_classic_commit lib/northbound_cli.c:49
    #11 0x56230376fb79 in nb_cli_pending_commit_check lib/northbound_cli.c:88
    #12 0x5623036c5bcb in cmd_execute_command_real lib/command.c:991
    #13 0x5623036c5f1b in cmd_execute_command lib/command.c:1053
    #14 0x5623036c6392 in cmd_execute lib/command.c:1221
    #15 0x5623037e75da in vty_command lib/vty.c:591
    #16 0x5623037e7a74 in vty_execute lib/vty.c:1354
    #17 0x5623037f0253 in vtysh_read lib/vty.c:2362
    #18 0x5623037db4e8 in event_call lib/event.c:1995
    #19 0x562303720f97 in frr_run lib/libfrr.c:1213
    #20 0x56230368615d in main pimd/pim6_main.c:184
    #21 0x7f360461bc86 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21c86)

Indirect leak of 96 byte(s) in 4 object(s) allocated from:
    #0 0x7f3605dbfd28 in __interceptor_calloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xded28)
    #1 0x56230373dd6b in qcalloc lib/memory.c:105
    #2 0x562303721651 in listnode_new lib/linklist.c:71
    #3 0x56230372182b in listnode_add lib/linklist.c:92
    #4 0x56230361ba9a in gm_join_new pimd/pim_iface.c:1295
    #5 0x56230361ba9a in pim_if_gm_join_add pimd/pim_iface.c:1326
    #6 0x562303642247 in lib_interface_gmp_address_family_static_group_create pimd/pim_nb_config.c:2868
    #7 0x562303767280 in nb_callback_create lib/northbound.c:1235
    #8 0x562303767280 in nb_callback_configuration lib/northbound.c:1579
    #9 0x562303768a1d in nb_transaction_process lib/northbound.c:1710
    #10 0x56230376904a in nb_candidate_commit_apply lib/northbound.c:1104
    #11 0x5623037692ba in nb_candidate_commit lib/northbound.c:1137
    #12 0x562303769dec in nb_cli_classic_commit lib/northbound_cli.c:49
    #13 0x56230376fb79 in nb_cli_pending_commit_check lib/northbound_cli.c:88
    #14 0x5623036c5bcb in cmd_execute_command_real lib/command.c:991
    #15 0x5623036c5f1b in cmd_execute_command lib/command.c:1053
    #16 0x5623036c6392 in cmd_execute lib/command.c:1221
    #17 0x5623037e75da in vty_command lib/vty.c:591
    #18 0x5623037e7a74 in vty_execute lib/vty.c:1354
    #19 0x5623037f0253 in vtysh_read lib/vty.c:2362
    #20 0x5623037db4e8 in event_call lib/event.c:1995
    #21 0x562303720f97 in frr_run lib/libfrr.c:1213
    #22 0x56230368615d in main pimd/pim6_main.c:184
    #23 0x7f360461bc86 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21c86)

Indirect leak of 48 byte(s) in 1 object(s) allocated from:
    #0 0x7f3605dbfd28 in __interceptor_calloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xded28)
    #1 0x56230373dd6b in qcalloc lib/memory.c:105
    #2 0x56230361b91d in gm_join_new pimd/pim_iface.c:1288
    #3 0x56230361b91d in pim_if_gm_join_add pimd/pim_iface.c:1326
    #4 0x562303642247 in lib_interface_gmp_address_family_static_group_create pimd/pim_nb_config.c:2868
    #5 0x562303767280 in nb_callback_create lib/northbound.c:1235
    #6 0x562303767280 in nb_callback_configuration lib/northbound.c:1579
    #7 0x562303768a1d in nb_transaction_process lib/northbound.c:1710
    #8 0x56230376904a in nb_candidate_commit_apply lib/northbound.c:1104
    #9 0x5623037692ba in nb_candidate_commit lib/northbound.c:1137
    #10 0x562303769dec in nb_cli_classic_commit lib/northbound_cli.c:49
    #11 0x56230376fb79 in nb_cli_pending_commit_check lib/northbound_cli.c:88
    #12 0x5623036c5bcb in cmd_execute_command_real lib/command.c:991
    #13 0x5623036c5f6f in cmd_execute_command lib/command.c:1072
    #14 0x5623036c6392 in cmd_execute lib/command.c:1221
    #15 0x5623037e75da in vty_command lib/vty.c:591
    #16 0x5623037e7a74 in vty_execute lib/vty.c:1354
    #17 0x5623037f0253 in vtysh_read lib/vty.c:2362
    #18 0x5623037db4e8 in event_call lib/event.c:1995
    #19 0x562303720f97 in frr_run lib/libfrr.c:1213
    #20 0x56230368615d in main pimd/pim6_main.c:184
    #21 0x7f360461bc86 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21c86)

Indirect leak of 24 byte(s) in 1 object(s) allocated from:
    #0 0x7f3605dbfd28 in __interceptor_calloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xded28)
    #1 0x56230373dd6b in qcalloc lib/memory.c:105
    #2 0x562303721651 in listnode_new lib/linklist.c:71
    #3 0x56230372182b in listnode_add lib/linklist.c:92
    #4 0x56230361ba9a in gm_join_new pimd/pim_iface.c:1295
    #5 0x56230361ba9a in pim_if_gm_join_add pimd/pim_iface.c:1326
    #6 0x562303642247 in lib_interface_gmp_address_family_static_group_create pimd/pim_nb_config.c:2868
    #7 0x562303767280 in nb_callback_create lib/northbound.c:1235
    #8 0x562303767280 in nb_callback_configuration lib/northbound.c:1579
    #9 0x562303768a1d in nb_transaction_process lib/northbound.c:1710
    #10 0x56230376904a in nb_candidate_commit_apply lib/northbound.c:1104
    #11 0x5623037692ba in nb_candidate_commit lib/northbound.c:1137
    #12 0x562303769dec in nb_cli_classic_commit lib/northbound_cli.c:49
    #13 0x56230376fb79 in nb_cli_pending_commit_check lib/northbound_cli.c:88
    #14 0x5623036c5bcb in cmd_execute_command_real lib/command.c:991
    #15 0x5623036c5f6f in cmd_execute_command lib/command.c:1072
    #16 0x5623036c6392 in cmd_execute lib/command.c:1221
    #17 0x5623037e75da in vty_command lib/vty.c:591
    #18 0x5623037e7a74 in vty_execute lib/vty.c:1354
    #19 0x5623037f0253 in vtysh_read lib/vty.c:2362
    #20 0x5623037db4e8 in event_call lib/event.c:1995
    #21 0x562303720f97 in frr_run lib/libfrr.c:1213
    #22 0x56230368615d in main pimd/pim6_main.c:184
    #23 0x7f360461bc86 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21c86)

SUMMARY: AddressSanitizer: 400 byte(s) leaked in 11 allocation(s).
***********************************************************************************
```

Signed-off-by: Keelan Cannoo <keelan.cannoo@icloud.com>