lib: Free memory correctly when braces used in parser

lib: Free memory correctly when braces used in parser

When braces (optional parameters) are used in the quagga parser, there
was a small leak on every iteration.  Since this construct is primarily
used in the configuation process rather than show commands, it was not
readily apparent.  With the addition of the "show ip bgp {json}" form of
the commands, each time one was run, memory was leaked.

Ticket: CM-11435
Signed-off-by: Don Slice
Reviewed By: Donald Sharp
Testing Done: Manual testing, bgp-min and bgp-smoke successful