zebra: Fix opaque memory leak in rare situation

[donaldsharp]

Fix this:
*********************************************************************************** Address Sanitizer Error detected in zebra_opaque.test_zebra_opaque/r3.asan.zebra.11099

================================================================= ==11099==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 66 byte(s) in 1 object(s) allocated from:
#0 0x7f527fc06b40 in __interceptor_malloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xdeb40)
#1 0x7f527f5e852b in qmalloc lib/memory.c:100
#2 0x56418d20832d in zread_route_add zebra/zapi_msg.c:2125
#3 0x56418d215d08 in zserv_handle_commands zebra/zapi_msg.c:4011
#4 0x56418d32ab5b in zserv_process_messages zebra/zserv.c:520
#5 0x7f527f6938d3 in event_call lib/event.c:2003
#6 0x7f527f5cb692 in frr_run lib/libfrr.c:1218
#7 0x56418d1c3336 in main zebra/main.c:508
#8 0x7f527e656c86 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21c86)

SUMMARY: AddressSanitizer: 66 byte(s) leaked in 1 allocation(s). ***********************************************************************************

Code inspection leads to some code paths where the opaque data was not freed up.

[mjstapp]

maybe it'd be good to take several of these common "re" memory free-ers and put them in one common function?

[donaldsharp]

I spent a few minutes trying to figure out how to make this better and frankly the whole thing needs to be reworked, which is far more than I want to do at this point in time. This function early_route_memory_free is already abstracted to handle all the freeing points in early_route_add/delete. Let's try to get the address sanitizer problem fixed and I will come back around in the future after I have some time to rework the whole thing