message: tf.data service treats 'grpc' data transfer protocol correctly
diff: @@ -139,7 +139,7 @@ Status WorkerGrpcDataServer::StartServiceInternal() {
  /*replace_all=*/false);
  std::string transfer_address = worker_address;
  std::string transfer_protocol = config_.data_transfer_protocol();
  - if (!transfer_protocol.empty()) {
  + if (!transfer_protocol.empty() && transfer_protocol != "grpc") {
  TF_RETURN_IF_ERROR(DataTransferServer::Build(
  transfer_protocol, service_->get_element_getter(), &transfer_server_));
  TF_RETURN_IF_ERROR(transfer_server_->Start());
  