Make node join event logging less noisy

Commit ca9a768d80
added a number of debugging messages for node join/leave
events.

This patch checks if a node already was listed,
and otherwise skips the logging to make the logs a bit
less noisy.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

libnetwork/networkdb/delegate.go

@@ -111,9 +111,12 @@ func (nDB *NetworkDB) handleNodeEvent(nEvent *NodeEvent) bool {
 	switch nEvent.Type {
 	case NodeEventTypeJoin:
 		nDB.Lock()
+		_, found := nDB.nodes[n.Name]
 		nDB.nodes[n.Name] = n
 		nDB.Unlock()
-		logrus.Infof("Node join event for %s/%s", n.Name, n.Addr)
+		if !found {
+			logrus.Infof("Node join event for %s/%s", n.Name, n.Addr)
+		}
 		return true
 	case NodeEventTypeLeave:
 		nDB.Lock()