cifs: use mod_delayed_work() for &server->reconnect if already queued

mod_delayed_work() is safer than queue_delayed_work() if there's a
chance that the work is already in the queue.
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/smb2pdu.c

@@ -389,7 +389,7 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon)
 	}
 
 	if (smb2_command != SMB2_INTERNAL_CMD)
-		queue_delayed_work(cifsiod_wq, &server->reconnect, 0);
+		mod_delayed_work(cifsiod_wq, &server->reconnect, 0);
 
 	atomic_inc(&tconInfoReconnectCount);
 out:
@@ -3570,7 +3570,7 @@ SMB2_echo(struct TCP_Server_Info *server)
 
 	if (server->tcpStatus == CifsNeedNegotiate) {
 		/* No need to send echo on newly established connections */
-		queue_delayed_work(cifsiod_wq, &server->reconnect, 0);
+		mod_delayed_work(cifsiod_wq, &server->reconnect, 0);
 		return rc;
 	}