Merge "Accept more than one test connection."

void TestEnvironment::SetUpTestChannel() {

  bool transport_configured = test_channel_transport_.SetUp(

      test_socket_server_, [this](std::shared_ptr<AsyncDataChannel> conn_fd,

                                  AsyncDataChannelServer*) {

                                  AsyncDataChannelServer* server) {

        LOG_INFO("Test channel connection accepted.");

        server->StartListening();

        if (test_channel_open_) {

          LOG_WARN("Only one connection at a time is supported");

          test_channel_transport_.SendResponse(conn_fd,