@Override
    public void stop() {
        super.stop();

        UserEventDispatcher.removeListener(this);
        MUCServicePropertyEventDispatcher.removeListener(this);

        // Remove the statistics.
        StatisticsManager.getInstance().removeStatistic(roomsStatKey);
        StatisticsManager.getInstance().removeStatistic(occupantsStatKey);
        StatisticsManager.getInstance().removeStatistic(usersStatKey);
        StatisticsManager.getInstance().removeStatistic(incomingStatKey);
        StatisticsManager.getInstance().removeStatistic(outgoingStatKey);

        for (MultiUserChatService service : mucServices.values()) {
            unregisterMultiUserChatService(service.getServiceName(), false);
        }
    }
Called when manager is stopped, to clean things up.
xmppserver/src/main/java/org/jivesoftware/openfire/muc/MultiUserChatManager.java