Merge "adb: don't error in handle_host_request if we can't acquire a transport." into pi-dev

    std::string error;

    atransport* t = acquire_one_transport(type, serial, transport_id, nullptr, &error);

    if (!t) {

        return SendFail(reply_fd, error);

        return -1;

    }

    int ret = handle_forward_request(service, t, reply_fd);