bgpd: Fix memory leak for `conf_copy()` - SoO ecommunity

bgpd: Fix memory leak for `conf_copy()` - SoO ecommunity

==1179738== 48 (40 direct, 8 indirect) bytes in 1 blocks are definitely lost in loss record 13 of 29
==1179738==    at 0x483AB65: calloc (vg_replace_malloc.c:760)
==1179738==    by 0x493C8D5: qcalloc (memory.c:116)
==1179738==    by 0x208F0C: ecommunity_dup (bgp_ecommunity.c:267)
==1179738==    by 0x2B300C: conf_copy (bgp_updgrp.c:170)
==1179738==    by 0x2B35BF: peer2_updgrp_copy (bgp_updgrp.c:277)
==1179738==    by 0x2B5189: update_group_find (bgp_updgrp.c:826)
==1179738==    by 0x2B70D0: update_group_adjust_peer (bgp_updgrp.c:1769)
==1179738==    by 0x23DB7D: update_group_adjust_peer_afs (bgp_updgrp.h:519)
==1179738==    by 0x243B21: bgp_establish (bgp_fsm.c:2129)
==1179738==    by 0x244B94: bgp_event_update (bgp_fsm.c:2597)
==1179738==    by 0x26B0E6: bgp_process_packet (bgp_packet.c:2895)
==1179738==    by 0x498F5FD: thread_call (thread.c:2008)
==1179738==    by 0x49253DA: frr_run (libfrr.c:1198)
==1179738==    by 0x1EEC38: main (bgp_main.c:520)

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>