isisd: fix _isis_spftree_del heap-use-after-free

isisd: fix _isis_spftree_del heap-use-after-free

Fix the following heap-use-after-free

> ==82961==ERROR: AddressSanitizer: heap-use-after-free on address 0x6020001e4750 at pc 0x55a8cc7f63ac bp 0x7ffd6948e340 sp 0x7ffd6948e330
> READ of size 8 at 0x6020001e4750 thread T0
>     #0 0x55a8cc7f63ab in isis_route_node_cleanup isisd/isis_route.c:335
>     #1 0x7ff25ec617c1 in route_node_free lib/table.c:75
>     #2 0x7ff25ec619fc in route_table_free lib/table.c:111
>     #3 0x7ff25ec61661 in route_table_finish lib/table.c:46
>     #4 0x55a8cc800d83 in _isis_spftree_del isisd/isis_spf.c:397
>     #5 0x55a8cc800e45 in isis_spftree_clear isisd/isis_spf.c:414
>     #6 0x55a8cc80bd9a in isis_run_spf isisd/isis_spf.c:2020
>     #7 0x55a8cc80c370 in isis_run_spf_with_protection isisd/isis_spf.c:2076
>     #8 0x55a8cc80cf52 in isis_run_spf_cb isisd/isis_spf.c:2165
>     #9 0x7ff25ec7c4dc in event_call lib/event.c:1970
>     #10 0x7ff25eb64423 in frr_run lib/libfrr.c:1213
>     #11 0x55a8cc7799da in main isisd/isis_main.c:318
>     #12 0x7ff25e623d8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
>     #13 0x7ff25e623e3f in __libc_start_main_impl ../csu/libc-start.c:392
>     #14 0x55a8cc778e44 in _start (/usr/lib/frr/isisd+0x109e44)
>
> 0x6020001e4750 is located 0 bytes inside of 16-byte region [0x6020001e4750,0x6020001e4760)
> freed by thread T0 here:
>     #0 0x7ff25f000537 in __interceptor_free ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:127
>     #1 0x7ff25eb9012e in qfree lib/memory.c:130
>     #2 0x55a8cc7f6485 in isis_route_table_info_free isisd/isis_route.c:351
>     #3 0x55a8cc800cf4 in _isis_spftree_del isisd/isis_spf.c:395
>     #4 0x55a8cc800e45 in isis_spftree_clear isisd/isis_spf.c:414
>     #5 0x55a8cc80bd9a in isis_run_spf isisd/isis_spf.c:2020
>     #6 0x55a8cc80c370 in isis_run_spf_with_protection isisd/isis_spf.c:2076
>     #7 0x55a8cc80cf52 in isis_run_spf_cb isisd/isis_spf.c:2165
>     #8 0x7ff25ec7c4dc in event_call lib/event.c:1970
>     #9 0x7ff25eb64423 in frr_run lib/libfrr.c:1213
>     #10 0x55a8cc7799da in main isisd/isis_main.c:318
>     #11 0x7ff25e623d8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
>
> previously allocated by thread T0 here:
>     #0 0x7ff25f000a57 in __interceptor_calloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:154
>     #1 0x7ff25eb8ffdc in qcalloc lib/memory.c:105
>     #2 0x55a8cc7f63eb in isis_route_table_info_alloc isisd/isis_route.c:343
>     #3 0x55a8cc80052a in _isis_spftree_init isisd/isis_spf.c:334
>     #4 0x55a8cc800e51 in isis_spftree_clear isisd/isis_spf.c:415
>     #5 0x55a8cc80bd9a in isis_run_spf isisd/isis_spf.c:2020
>     #6 0x55a8cc80c370 in isis_run_spf_with_protection isisd/isis_spf.c:2076
>     #7 0x55a8cc80cf52 in isis_run_spf_cb isisd/isis_spf.c:2165
>     #8 0x7ff25ec7c4dc in event_call lib/event.c:1970
>     #9 0x7ff25eb64423 in frr_run lib/libfrr.c:1213
>     #10 0x55a8cc7799da in main isisd/isis_main.c:318
>     #11 0x7ff25e623d8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58

Fixes: 7153c3cabf ("isisd: update struct isis_route_info has multiple sr info by algorithm")
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>