long listNumDefinedQuotas(Connection conn) throws IOException {
    try (QuotaRetriever scanner = new QuotaRetriever(conn)) {
      return Iterables.size(scanner);
    }
  }
Returns the number of quotas defined in the HBase quota table.
hbase-server/src/test/java/org/apache/hadoop/hbase/quotas/SpaceQuotaHelperForTests.java