NFS and NFSv4 mounts can now share server address sanity checking.  And, it
provides an easy mechanism for adding IPv6 address checking at some later
point.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: Aurelien Charbon <aurelien.charbon@ext.bull.net>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>