message: Fix hello-ferris tests
diff: @@ -433,6 +433,16 @@ mod example {
  runtime.install(&EXAMPLE_HELLO_FERRIS_NPK).await?;
  runtime.start(EXAMPLE_HELLO_FERRIS).await?;
  assume("Hello once more from 0.0.1!", 5).await?;
  + // The hello-ferris example terminates after printing something.
  + // Wait for the notification that it stopped, otherwise the runtime
  + // will try to shutdown the application which is already exited.
  + runtime
  + .assume_notification(
  + |n| matches!(n, Notification::Exit(_, ExitStatus::Exit(0))),
  + 15,
  + )
  + .await?;
  +
  runtime.shutdown().await
  });
  