message: fscache: print error message when nydusd can't start
  At present, nydusd says nothing before exit. It's
  better to give users and developers a message about
  what't going on.
diff: @@ -699,7 +699,10 @@ fn process_daemon_arguments(
  bti: BuildTimeInfo,
  ) -> Result<()> {
  info!("Start Nydus in daemon mode!");
  - let daemon = create_daemon(subargs, bti)?;
  + let daemon = create_daemon(subargs, bti).map_err(|e| {
  + error!("Failed to start daemon: {}", e);
  + e
  + })?;
  DAEMON_CONTROLLER.set_daemon(daemon);
  Ok(())
  }
  