bgpd: Fix memory leak of some "show ip bgp neighbor" commands

sockunion_str2su() use is prone to memory leaks. Remove it's use all over
the code.

At least these commands leaked a sockunion union:
    - show ip bgp vpnv4 ... routes
    - show ip bgp ... received prefix-filter

Signed-off-by: Jorge Boncompte [DTI2] <jorge@dti2.net>
Signed-off-by: David Lamparter <equinox@diac24.net>
6 files changed