StorageUsageRefresher.Listener getUsageRefresherListener() {
    return containerStorageUsage -> {
      logger.trace("UsageRefresherListener invoked with new container storage usage");
      logger.debug("New usage: {}", containerStorageUsage);
      initMap(containerStorageUsage, this.storageUsages);
    };
  }
Return a {@link StorageUsageRefresher.Listener}, only used in test.
@return {@link StorageUsageRefresher.Listener}.
ambry-quota/src/main/java/com/github/ambry/quota/storage/StorageQuotaEnforcer.java