ospf6d: Fixing memory leak in ospf6_lsa_create_headeronly for both master and slave.

ospf6d: Fixing memory leak in ospf6_lsa_create_headeronly for both master and slave.

Problem Statement:
=================
Memory leak backtraces

2022-11-23 01:51:10,525 - ERROR: ==842== 1,100 (1,000 direct, 100 indirect) bytes in 5 blocks are definitely lost in loss record 29 of 31
2022-11-23 01:51:10,525 - ERROR: ==842==    at 0x4C31FAC: calloc (vg_replace_malloc.c:762)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x4E8A1BF: qcalloc (memory.c:111)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x13555A: ospf6_lsa_alloc (ospf6_lsa.c:723)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x1355F3: ospf6_lsa_create_headeronly (ospf6_lsa.c:756)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x135702: ospf6_lsa_copy (ospf6_lsa.c:790)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x13B64B: ospf6_dbdesc_recv_slave (ospf6_message.c:976)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x13B64B: ospf6_dbdesc_recv (ospf6_message.c:1038)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x13B64B: ospf6_read_helper (ospf6_message.c:1838)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x13B64B: ospf6_receive (ospf6_message.c:1875)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x4EB741B: thread_call (thread.c:1692)
2022-11-23 01:51:10,526 - ERROR: ==842==    by 0x4E85B17: frr_run (libfrr.c:1068)
2022-11-23 01:51:10,526 - ERROR: ==842==    by 0x119585: main (ospf6_main.c:228)
2022-11-23 01:51:10,526 - ERROR: ==842==

2022-11-23 01:51:10,524 - ERROR: Found memory leak in module ospf6d
2022-11-23 01:51:10,525 - ERROR: ==842== 220 (200 direct, 20 indirect) bytes in 1 blocks are definitely lost in loss record 21 of 31
2022-11-23 01:51:10,525 - ERROR: ==842==    at 0x4C31FAC: calloc (vg_replace_malloc.c:762)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x4E8A1BF: qcalloc (memory.c:111)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x13555A: ospf6_lsa_alloc (ospf6_lsa.c:723)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x1355F3: ospf6_lsa_create_headeronly (ospf6_lsa.c:756)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x135702: ospf6_lsa_copy (ospf6_lsa.c:790)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x13BBCE: ospf6_dbdesc_recv_master (ospf6_message.c:760)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x13BBCE: ospf6_dbdesc_recv (ospf6_message.c:1036)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x13BBCE: ospf6_read_helper (ospf6_message.c:1838)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x13BBCE: ospf6_receive (ospf6_message.c:1875)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x4EB741B: thread_call (thread.c:1692)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x4E85B17: frr_run (libfrr.c:1068)
2022-11-23 01:51:10,525 - ERROR: ==842==    by 0x119585: main (ospf6_main.c:228)
2022-11-23 01:51:10,525 - ERROR: ==842==

RCA:
====
These memory leaks are beacuse of last lsa in neighbour's request_list is not
getting freed beacuse of lsa lock. The last request has an addtional lock which
is added as a part of ospf6_make_lsreq, this lock needs to be removed
in order for the lsa to get freed.

Fix:
====
Check and remove the lock on the last request in all the functions.

Signed-off-by: Manoj Naragund <mnaragund@vmware.com>