@Override
  public boolean isReady() {
    return isReady.get();
  }
Constructor for {@link AmbryCUQuotaSource}.
@param quotaConfig {@link QuotaConfig} object.
@param accountService {@link AccountService} object.
@param quotaMetrics {@link QuotaMetrics} object.
@param routerConfig {@link RouterConfig} object.
@throws IOException in case of any exception.
ambry-quota/src/main/java/com/github/ambry/quota/capacityunit/AmbryCUQuotaSource.java