bgpd : multiple memory leak fixes in show commands

bgpd : multiple memory leak fixes in show commands

Issue: bgpd got kill due to out of memory, when show bgp
neighbor json and show ip bgp neighbor <ip> routes json
commands executed multiple times in a setup having 320554
routes.

RCA: Heap allocated for bgpd keeps increasing. This is verified
using top command and show memory command.

Memleak Fix-1: show ip bgp route json command
When dumping a large bit of table data via bgp_show_route
and if there is no information to display for a particular
struct bgp_node *` the data allocated via json_object_new_array()
is not freed. This is resolved now.

Memleak Fix-2:
The function bgp_peer_counts() doesn't free the memory allocated for
json_loop when there is No such neighbor or address family. This is
fixed now.

Signed-off-by: Sarita Patra <saritap@vmware.com>