clean-up unit tests

modules/RTC/MockClasses.js

         return Promise.resolve(/* answer */{});
     }
 
-
     /**
      * {@link TraceablePeerConnection.setLocalDescription}.
      *

modules/xmpp/ChatRoom.spec.js

                 'jid',
                 'password',
                 xmpp,
-                { preferredCodec: 'vp8' } /* options */);
+                {} /* options */);
             emitterSpy = spyOn(room.eventEmitter, 'emit');
         });
         it('parses status correctly', () => {