Merge "init: Cleanly exit subcontext processes upon init's death"

Result<std::string> ReadMessage(int socket) {

    char buffer[kBufferSize] = {};

    auto result = TEMP_FAILURE_RETRY(recv(socket, buffer, sizeof(buffer), 0));

    if (result <= 0) {

    if (result == 0) {

        return Error();

    } else if (result < 0) {

        return ErrnoError();

    }

    return std::string(buffer, result);

        auto init_message = ReadMessage(init_fd_);

        if (!init_message) {

            if (init_message.error_errno() == 0) {

                // If the init file descriptor was closed, let's exit quietly. If

                // this was accidental, init will restart us. If init died, this

                // avoids calling abort(3) unnecessarily.

                return;

            }

            LOG(FATAL) << "Could not read message from init: " << init_message.error();

        }