When IPv6 peer BFD down status is received by BGP, all the the peers for which the...

When IPv6 peer BFD down status is received by BGP, all the the peers for which the BFD is enabled are brought down. This happens due to reverse memcmp check of destination and source IPv6 addresses with the BFD enabled BGP peers. Fixed it by doing the memcmp correctly.

Also, there is no reason stored in the last_reset field when BGP peer goes down due BFD. Incorrect/no peer down reason can get logged when BGP peer goes down due to BFD. Fixed it by adding new BFD peer down reason code and storing it in the peer last_reset field when peer is broght down due to BFD.