NSM: Check result of SM_UNMON upcall

Make sure any error returned by rpc.statd during an SM_UNMON call is
reported rather than ignored completely.  There isn't much to do with
such an error, but we should log it in any case.

Similar to a recent change to nsm_monitor().
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

fs/lockd/mon.c

@@ -126,6 +126,8 @@ void nsm_unmonitor(const struct nlm_host *host)
 		dprintk("lockd: nsm_unmonitor(%s)\n", nsm->sm_name);
 
 		status = nsm_mon_unmon(nsm, SM_UNMON, &res);
+		if (res.status != 0)
+			status = -EIO;
 		if (status < 0)
 			printk(KERN_NOTICE "lockd: cannot unmonitor %s\n",
 					nsm->sm_name);