pimd: fix a possible use after free bug when doing pim trace

```
ERROR: AddressSanitizer: heap-use-after-free on address 0x6160000aecf0 at pc 0x5555557ecdb9 bp 0x7fffffffe350 sp 0x7fffffffe340
READ of size 4 at 0x6160000aecf0 thread T0
    #0 0x5555557ecdb8 in igmp_source_delete pimd/pim_igmpv3.c:340
    FRRouting#1 0x5555557ed475 in igmp_source_delete_expired pimd/pim_igmpv3.c:405
    FRRouting#2 0x5555557de574 in igmp_group_timer pimd/pim_igmp.c:1346
    FRRouting#3 0x7ffff7275421 in event_call lib/event.c:1996
    FRRouting#4 0x7ffff7140797 in frr_run lib/libfrr.c:1237
    FRRouting#5 0x5555557f5840 in main pimd/pim_main.c:166
    FRRouting#6 0x7ffff6a54082 in __libc_start_main ../csu/libc-start.c:308
    FRRouting#7 0x555555686eed in _start (/usr/lib/frr/pimd+0x132eed)

0x6160000aecf0 is located 112 bytes inside of 600-byte region [0x6160000aec80,0x6160000aeed8)
freed by thread T0 here:
    #0 0x7ffff767b40f in __interceptor_free ../../../../src/libsanitizer/asan/asan_malloc_linux.cc:122
    FRRouting#1 0x7ffff716ed34 in qfree lib/memory.c:131
    FRRouting#2 0x5555557169ae in pim_channel_oil_free pimd/pim_oil.c:84
    FRRouting#3 0x555555717981 in pim_channel_oil_del pimd/pim_oil.c:199
    FRRouting#4 0x55555573c42c in tib_sg_gm_prune pimd/pim_tib.c:196
    FRRouting#5 0x5555557d6d04 in igmp_source_forward_stop pimd/pim_igmp.c:229
    FRRouting#6 0x5555557d5855 in igmp_anysource_forward_stop pimd/pim_igmp.c:61
    FRRouting#7 0x5555557de539 in igmp_group_timer pimd/pim_igmp.c:1344
    FRRouting#8 0x7ffff7275421 in event_call lib/event.c:1996
    FRRouting#9 0x7ffff7140797 in frr_run lib/libfrr.c:1237
    FRRouting#10 0x5555557f5840 in main pimd/pim_main.c:166
    FRRouting#11 0x7ffff6a54082 in __libc_start_main ../csu/libc-start.c:308

previously allocated by thread T0 here:
    #0 0x7ffff767ba06 in __interceptor_calloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cc:153
    FRRouting#1 0x7ffff716ebe1 in qcalloc lib/memory.c:106
    FRRouting#2 0x555555716eb7 in pim_channel_oil_add pimd/pim_oil.c:133
    FRRouting#3 0x55555573b2b9 in tib_sg_oil_setup pimd/pim_tib.c:30
    FRRouting#4 0x55555573bdd3 in tib_sg_gm_join pimd/pim_tib.c:119
    FRRouting#5 0x5555557d6788 in igmp_source_forward_start pimd/pim_igmp.c:193
    FRRouting#6 0x5555557d5771 in igmp_anysource_forward_start pimd/pim_igmp.c:51
    FRRouting#7 0x5555557ecaa0 in group_exclude_fwd_anysrc_ifempty pimd/pim_igmpv3.c:310
    FRRouting#8 0x5555557ef937 in toex_incl pimd/pim_igmpv3.c:839
    FRRouting#9 0x5555557f00a2 in igmpv3_report_toex pimd/pim_igmpv3.c:938
    FRRouting#10 0x5555557f543d in igmp_v3_recv_report pimd/pim_igmpv3.c:2000
    FRRouting#11 0x5555557da2b4 in pim_igmp_packet pimd/pim_igmp.c:787
    FRRouting#12 0x5555556ee46a in process_igmp_packet pimd/pim_mroute.c:763
    FRRouting#13 0x5555556ee5f3 in pim_mroute_msg pimd/pim_mroute.c:787
    FRRouting#14 0x5555556eef58 in mroute_read pimd/pim_mroute.c:877
    FRRouting#15 0x7ffff7275421 in event_call lib/event.c:1996
    FRRouting#16 0x7ffff7140797 in frr_run lib/libfrr.c:1237
    FRRouting#17 0x5555557f5840 in main pimd/pim_main.c:166
    FRRouting#18 0x7ffff6a54082 in __libc_start_main ../csu/libc-start.c:308

SUMMARY: AddressSanitizer: heap-use-after-free pimd/pim_igmpv3.c:340 in igmp_source_delete
Shadow bytes around the buggy address:
  0x0c2c8000dd40: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c8000dd50: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c8000dd60: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c8000dd70: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c8000dd80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c2c8000dd90: fd fd fd fd fd fd fd fd fd fd fd fd fd fd[fd]fd
  0x0c2c8000dda0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c8000ddb0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c8000ddc0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c8000ddd0: fd fd fd fd fd fd fd fd fd fd fd fa fa fa fa fa
  0x0c2c8000dde0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
  Shadow gap:              cc
```

Signed-off-by: Jafar Al-Gharaibeh <jafar@atcorp.com>

pimd/pim_tib.c

@@ -193,5 +193,5 @@ void tib_sg_gm_prune(struct pim_instance *pim, pim_sgaddr sg,
 	 */
 	pim_ifchannel_local_membership_del(oif, &sg);
 
-	pim_channel_oil_del(*oilp, __func__);
+	*oilp = pim_channel_oil_del(*oilp, __func__);
 }