private List<HiveRoleGrant> getCurrentRoles() throws HiveAuthzPluginException {
    initUserRoles();
    return currentRoles;
  }
Convert metastore object type to HivePrivilegeObjectType.
Also verifies that metastore object type is of a type on which metastore privileges are
supported by sql std auth.
@param objectType
@return corresponding HivePrivilegeObjectType
ql/src/java/org/apache/hadoop/hive/ql/security/authorization/plugin/sqlstd/SQLStdHiveAccessController.java