private void createDefaultRoles() throws MetaException {
    try {
      createDefaultRoles_core();
    } catch (JDOException e) {
      LOG.warn("Retrying creating default roles after error: " + e.getMessage(), e);
      createDefaultRoles_core();
    }
  }
create default roles if they don't exist.

This is a potential contention when HiveServer2 using embedded metastore and Metastore
Server try to concurrently invoke createDefaultRoles. If one failed, JDOException was caught
for one more time try, if failed again, simply ignored by warning, which meant another
succeeds.

@throws MetaException
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/HMSHandler.java