add more logging around attaching videos to thumbnails

modules/UI/videolayout/RemoteVideo.js

 
 RemoteVideo.prototype.addRemoteStreamElement = function(stream) {
     if (!this.container) {
+        logger.debug('Not attaching remote stream due to no container');
+
         return;
     }
 
     }
 
     if (!stream.getOriginalStream()) {
+        logger.debug('Remote video stream has no original stream');
+
         return;
     }
 

modules/UI/videolayout/VideoLayout.js

         const id = stream.getParticipantId();
         const remoteVideo = remoteVideos[id];
 
+        logger.debug(`Received a new ${stream.getType()} stream for ${id}`);
+
         if (!remoteVideo) {
+            logger.debug('No remote video element to add stream');
+
             return;
         }