shim: abort setup on failed start and process exit

Shim setup listens on a socket in the process share, if shim setup hasn't happened on exit revert will fail. This change makes sure shim setup is aborted on a doomed launch.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

internal/app/app.go

@@ -24,6 +24,8 @@ type app struct {
 	id *ID
 	// underlying user switcher process
 	cmd *exec.Cmd
+	// shim setup abort reason and completion
+	abort chan error
 	// child process related information
 	seal *appSeal
 	// error returned waiting for process