NFS: Show "nointr" mount option

The default "intr" setting is different for NFS and NFSv4.  To avoid
confusion on this issue, don't hide the "nointr" option in /proc/mounts.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>