row_discard_tablespace_for_mysql() can unlock data dictionary without locking data dictionary

if (fts_exist)

  {     

    fts_optimize_remove_table(table);

    purge_sys.stop_FTS(*table);

    err= fts_lock_tables(trx, *table);

    if (err != DB_SUCCESS)

    {

rollback:

      if (fts_exist)

      {

        purge_sys.resume_FTS();

        fts_optimize_add_table(table);

      } 

      trx->rollback();

      row_mysql_unlock_data_dictionary(trx);

      return err;

    }

  }

  row_mysql_lock_data_dictionary(trx);

  trx->op_info = "discarding tablespace";

  trx->dict_operation= true;

  /* We serialize data dictionary operations with dict_sys.latch:

  this is to avoid deadlocks during data dictionary operations */

  err= row_discard_tablespace_foreign_key_checks(trx, table);

  if (err != DB_SUCCESS)

    goto rollback;