message: fix index failed but return succeed
diff: @@ -23,7 +23,7 @@ void AdminTaskProcessor::process(const cpp2::AddAdminTaskRequest& req) {
  default:
  LOG(ERROR) << "unsupported conversion of code "
  << cpp2::_ErrorCode_VALUES_TO_NAMES.at(storageCode);
  - return meta::cpp2::ErrorCode::SUCCEEDED;
  + return meta::cpp2::ErrorCode::E_UNKNOWN;
  }
  };
  