mount.cifs: allow mounts to ipv6 capable servers

mount.cifs: allow mounts to ipv6 capable servers

The current name resolution scheme in mount.cifs is IPv4 only. Expand
it to be protocol-independent. Also take advantage of the fact that
getaddrinfo() returns a list of addresses and have mount.cifs try each
in turn until it hits one that's reachable and allows the socket to
connect.

Signed-off-by: Jeff Layton <jlayton@redhat.com>