QuotaCache should cancel the QuotaRefresherChore service inside its stop()

    // Stop the quota manager
    if (rsQuotaManager != null) {
      rsQuotaManager.stop();
    }

  public void stop() {
    if (isQuotaEnabled()) {
      quotaCache.stop("shutdown");
    }
  }

  public void start() throws IOException {
    stopped = false;

    // TODO: This will be replaced once we have the notification bus ready.
    Configuration conf = rsServices.getConfiguration();
    int period = conf.getInt(REFRESH_CONF_KEY, REFRESH_DEFAULT_PERIOD);
    refreshChore = new QuotaRefresherChore(period, this);
    rsServices.getChoreService().scheduleChore(refreshChore);
  }

  @Override
  public void stop(final String why) {
    stopped = true;
  }