Moves JingleSessionPC initialization from ChatRoom to JitsiConference

JitsiConference.js

         if (conference.room.isFocus(jingleSession.peerjid)) {
             // Accept incoming call
             conference.room.setJingleSession(jingleSession);
+            jingleSession.initialize(false /* initiator */, conference.room);
             conference.rtc.onIncommingCall(jingleSession);
             jingleSession.acceptOffer(jingleOffer, null,
                 function (error) {

modules/xmpp/ChatRoom.js

 
 ChatRoom.prototype.setJingleSession = function(session){
     this.session = session;
-    this.session.initialize(false /* initiator */, this /* room */);
 };