If portmap is not listening on UDP (as apparently happens with

MS-Windows-Server2003R2SP2), then nfs mounts have to be mounted
with -o mountproto=tcp to succeed.

In this case a umount will still try UDP and will fail to contact the
server.  It will still succeed with the local unmount (after a
timeout) but exits with a non-zero exit status.  This causes
/bin/mount to retry so we get a strange error about the filesystem
not being mounted.

So:
  get umount to use tcp if "mountproto=tcp" appears in mtab
  ignore any failure message from the server that would overwrite
     a success message from the local umount syscall.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Steve Dickson <steved@redhat.com>