bgpd: fix bgp_pbr_match_entry memory leak

bgpd: fix bgp_pbr_match_entry memory leak

> ==238132==ERROR: LeakSanitizer: detected memory leaks
>
> Direct leak of 160 byte(s) in 1 object(s) allocated from:
>     #0 0x7fd79f0b4a57 in __interceptor_calloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:154
>     #1 0x7fd79ea6f8dd in qcalloc lib/memory.c:105
>     #2 0x5586b26995f9 in bgp_pbr_match_entry_alloc_intern bgpd/bgp_pbr.c:1155
>     #3 0x7fd79ea17d79 in hash_get lib/hash.c:147
>     #4 0x5586b26a551d in bgp_pbr_policyroute_add_to_zebra_unit bgpd/bgp_pbr.c:2522
>     #5 0x5586b26a6436 in bgp_pbr_policyroute_add_to_zebra bgpd/bgp_pbr.c:2672
>     #6 0x5586b26a8089 in bgp_pbr_handle_entry bgpd/bgp_pbr.c:2876
>     #7 0x5586b26a8912 in bgp_pbr_update_entry bgpd/bgp_pbr.c:2939
>     #8 0x5586b2829472 in bgp_zebra_announce bgpd/bgp_zebra.c:1618
>     #9 0x5586b282ab4b in bgp_zebra_announce_table bgpd/bgp_zebra.c:1766
>     #10 0x5586b2824b99 in bgp_zebra_tm_connect bgpd/bgp_zebra.c:1091
>     #11 0x7fd79eb7798e in event_call lib/event.c:2011
>     #12 0x7fd79ea42ff1 in frr_run lib/libfrr.c:1216
>     #13 0x5586b2503a15 in main bgpd/bgp_main.c:545
>     #14 0x7fd79e429d8f 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>