nfsd: Fix message level for normal termination

The warning message from nfsd terminating normally
can confuse system adminstrators or monitoring software.

Though it's not exactly fair to pin-point a commit where it
originated, the current form in the current place started
to appear in:

Fixes: e096bbc648 ("knfsd: remove special handling for SIGHUP")
Signed-off-by: kazuo ito <kzpn200@gmail.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfssvc.c

@@ -529,8 +529,7 @@ static void nfsd_last_thread(struct svc_serv *serv, struct net *net)
 		return;
 
 	nfsd_shutdown_net(net);
-	printk(KERN_WARNING "nfsd: last server has exited, flushing export "
-			    "cache\n");
+	pr_info("nfsd: last server has exited, flushing export cache\n");
 	nfsd_export_flush(net);
 }