libpod: rework shutdown handler flow

Currently podman run -d can exit 0 if we send SIGTERM during startup
even though the contianer was never started. That just doesn't make any
sense is horribly confusing for a external job manager like systemd.

The original motivation was to exit 0 for the podman.service in commit
ca7376bb11. That does make sense but it should only do so for the
service and only if the server did indeed gracefully shutdown.

So we rework how the exit logic works, do not let the handler perform
the exit. Instead the shutdown package does the exit after all handlers
are run, this solves the issue of ordering. Then we default to exit code
1 like we did before and allow the service exit handler to overwrite the
exit code 0 in case of a graceful shutdown.

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

libpod/runtime.go

@@ -218,11 +218,6 @@ func newRuntimeFromConfig(ctx context.Context, conf *config.Config, options ...R
 		if runtime.store != nil {
 			_, _ = runtime.store.Shutdown(false)
 		}
-		// For `systemctl stop podman.service` support, exit code should be 0
-		if sig == syscall.SIGTERM {
-			os.Exit(0)
-		}
-		os.Exit(1)
 		return nil
 	}); err != nil && !errors.Is(err, shutdown.ErrHandlerExists) {
 		logrus.Errorf("Registering shutdown handler for libpod: %v", err)