dlm: keep listening connection alive with sctp mode

The connection struct with nodeid 0 is the listening socket,
not a connection to another node.  The sctp resend function
was not checking that the nodeid was valid (non-zero), so it
would mistakenly get and resend on the listening connection
when nodeid was zero.
Signed-off-by: Lidong Zhong <lzhong@suse.com>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/lowcomms.c

@@ -617,6 +617,11 @@ static void retry_failed_sctp_send(struct connection *recv_con,
 	int nodeid = sn_send_failed->ssf_info.sinfo_ppid;
 
 	log_print("Retry sending %d bytes to node id %d", len, nodeid);
+	
+	if (!nodeid) {
+		log_print("Shouldn't resend data via listening connection.");
+		return;
+	}
 
 	con = nodeid2con(nodeid, 0);
 	if (!con) {