bgpd: Prevent IPv6 routes received via a ibgp session with own ip as nexthop

bgpd: Prevent IPv6 routes received via a ibgp session with own ip as nexthop

Prevent IPv6 routes received via a ibgp session with one of its own interface
ip as nexthop from getting installed in the BGP table.

Implemented IPV6 HASH table, where we need to add any ipv6 address as they
gets configured and delete them from the HASH table as the ipv6 addresses
get unconfigured. The above hash table is used to verify if any route learned
via BGP has nexthop which is equal to one of its its connected ipv6 interface.

Signed-off-by: Biswajit Sadhu sadhub@vmware.com