fix: Cleans up rooms after failure to join.

Subsequent attempts to join will show produce an error "[JitsiConference.js] : A coference with the same name has already been created!".

JitsiConferenceEventManager.js

     this.chatRoomForwarder.forward(XMPPEvents.RESERVATION_ERROR,
         JitsiConferenceEvents.CONFERENCE_FAILED,
         JitsiConferenceErrors.RESERVATION_ERROR);
+    chatRoom.addListener(XMPPEvents.RESERVATION_ERROR,
+        () => {
+            conference.xmpp.connection.emuc.doLeave(conference.room.roomjid);
+        });
 
     this.chatRoomForwarder.forward(XMPPEvents.GRACEFUL_SHUTDOWN,
         JitsiConferenceEvents.CONFERENCE_FAILED,

modules/xmpp/ChatRoom.js

             logger.warn('Maximum users limit for the room has been reached',
                 pres);
             this.eventEmitter.emit(XMPPEvents.ROOM_MAX_USERS_ERROR);
+            this.connection.emuc.doLeave(this.roomjid);
         } else if ($(pres)
             .find(
                 '>error[type="auth"]'