bgpd: Fix memory leak in json output of show commands
When dumping a large bit of table data via bgp_show_table
and if there is no information to display for a particular
`struct bgp_node *` the data allocated via json_object_new_array()
is leaked. Not a big deal on small tables but if you have a full
bgp feed and issue a show command that does not match any of
the route nodes ( say `vtysh -c "show bgp ipv4 large-community-list FOO"`)
then we will leak memory.
Before code change and issuing the above show bgp large-community-list command 15-20 times:
Memory statistics for bgpd:
System allocator statistics:
Total heap allocated: > 2GB
Holding block headers: 0 bytes
Used small blocks: 0 bytes
Used ordinary blocks: > 2GB
Free small blocks: 31 MiB
Free ordinary blocks: 616 KiB
Ordinary blocks: 0
Small blocks: 0
Holding blocks: 0
After:
Memory statistics for bgpd:
System allocator statistics:
Total heap allocated: 924 MiB
Holding block headers: 0 bytes
Used small blocks: 0 bytes
Used ordinary blocks: 558 MiB
Free small blocks: 26 MiB
Free ordinary blocks: 340 MiB
Ordinary blocks: 0
Small blocks: 0
Holding blocks: 0
Please note the 340mb of free ordinary blocks is from the fact I issued a
`show bgp ipv4 uni json` command and generated a large amount of data.
Fixes: #5445 Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>