private void updateOnlyMachineQuotaFactors() {
      Optional<Integer> rsSize = regionServersSize.get();
      if (rsSize.isPresent()) {
        updateMachineQuotaFactors(rsSize.get());
      } else {
        regionServersSize.refresh();
      }
    }
This method is cheaper than {@link #updateTableMachineQuotaFactors()} and should be used if
we don't have any table quotas in the cache.
hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/QuotaCache.java