fix(conference): Do not signal muted tracks on join.

Do not add the muted audio/video tracks to the peerconnection on join. The tracks will be added when the user unmutes for the first time. This reduces the number of remote sources that will be added when a participant joins a large call where everyone joins muted (startAudioMuted/startVideoMuted setting).

JitsiConference.js

     this.eventEmitter.emit(JitsiConferenceEvents.TRACK_MUTE_CHANGED, track, actorParticipant);
 };
 
+/**
+ * Returns the list of local tracks that need to be added to the peerconnection on join.
+ * This takes the startAudioMuted/startVideoMuted flags into consideration since we do not
+ * want to add the tracks if the user joins the call audio/video muted. The tracks will be
+ * added when the user unmutes for the first time.
+ * @returns {Array<JitsiLocalTrack>} - list of local tracks that are unmuted.
+ */
+JitsiConference.prototype._getInitialLocalTracks = function() {
+    return this.getLocalTracks()
+        .filter(track => (track.getType() === MediaType.AUDIO && !this.isStartAudioMuted())
+        || (track.getType() === MediaType.VIDEO && !this.isStartVideoMuted()));
+};
+
 /**
  * Clear JitsiLocalTrack properties and listeners.
  * @param track the JitsiLocalTrack object.
     // Open a channel with the videobridge.
     this._setBridgeChannel(jingleOffer, jingleSession.peerconnection);
 
-    // Add local tracks to the session
-    const localTracks = this.getLocalTracks();
+    const localTracks = this._getInitialLocalTracks();
 
     try {
         jingleSession.acceptOffer(
         this.p2pJingleSession.peerconnection,
         remoteID);
 
-    const localTracks = this.getLocalTracks();
+    const localTracks = this._getInitialLocalTracks();
 
     this.p2pJingleSession.acceptOffer(
         jingleOffer,
         this.p2pJingleSession.peerconnection,
         remoteID);
 
-    // NOTE one may consider to start P2P with the local tracks detached,
-    // but no data will be sent until ICE succeeds anyway. And we switch
-    // immediately once the P2P ICE connects.
-    const localTracks = this.getLocalTracks();
+    const localTracks = this._getInitialLocalTracks();
 
     this.p2pJingleSession.invite(localTracks);
 };