bgpd: fix bgp_pbr_match memory leak

bgpd: fix bgp_pbr_match memory leak

> Direct leak of 1144 byte(s) in 13 object(s) allocated from:
>     #0 0x7f3eedeb4a57 in __interceptor_calloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:154
>     #1 0x7f3eed86f8dd in qcalloc lib/memory.c:105
>     #2 0x55b32d236faf in bgp_pbr_match_alloc_intern bgpd/bgp_pbr.c:1074
>     #3 0x7f3eed817d79 in hash_get lib/hash.c:147
>     #4 0x55b32d242d9a in bgp_pbr_policyroute_add_to_zebra_unit bgpd/bgp_pbr.c:2486
>     #5 0x55b32d244436 in bgp_pbr_policyroute_add_to_zebra bgpd/bgp_pbr.c:2672
>     #6 0x55b32d245a05 in bgp_pbr_handle_entry bgpd/bgp_pbr.c:2843
>     #7 0x55b32d246912 in bgp_pbr_update_entry bgpd/bgp_pbr.c:2939
>     #8 0x55b32d3c7472 in bgp_zebra_announce bgpd/bgp_zebra.c:1618
>     #9 0x55b32d26e5e7 in bgp_process_main_one bgpd/bgp_route.c:3691
>     #10 0x55b32d26f77d in process_subq_other_route bgpd/bgp_route.c:3856
>     #11 0x55b32d2701ff in process_subq bgpd/bgp_route.c:3955
>     #12 0x55b32d27029f in meta_queue_process bgpd/bgp_route.c:3980
>     #13 0x7f3eed99fdd8 in work_queue_run lib/workqueue.c:282
>     #14 0x7f3eed97798e in event_call lib/event.c:2011
>     #15 0x7f3eed842ff1 in frr_run lib/libfrr.c:1216
>     #16 0x55b32d0a1a15 in main bgpd/bgp_main.c:545
>     #17 0x7f3eed229d8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58

Fixes: d114b0d739 ("bgpd: inject policy route entry from bgp into zebra pbr entries.")
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>