when a channel is update propagate the channel to everybody (#6677)

app/channel.go

@@ -281,6 +281,11 @@ func UpdateChannel(channel *model.Channel) (*model.Channel, *model.AppError) {
 		return nil, result.Err
 	} else {
 		InvalidateCacheForChannel(channel)
+
+		messageWs := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_CHANNEL_UPDATED, "", channel.Id, "", nil)
+		messageWs.Add("channel", channel.ToJson())
+		Publish(messageWs)
+
 		return channel, nil
 	}
 }