Fix for using IPv6 addresses with RDMA:

IPv6 addresses has a scope ID which sometimes is stored in the
"sin6_scope_id" field of "struct sockaddr_in6" and sometimes as part
of the IPv6 address itself depending on the context. If the scope ID
is not in the expected location, the IPv6 address lookups in the
so-called GID table will fail. Some code factoring has been made to
achieve a clean exit of the "addr_resolve" function via a common
"done" label.

Sponsored by: Mellanox Technologies
Submitted by: Shani Michaeli <shanim@mellanox.com>
MFC after: 1 week