fix: silence stderr when checking for ufw on debian systems
fix: silence stderr when checking for ufw on debian systems

Closes #4710

claytonbrown/dokku,claytonbrown/dokku,dokku/dokku,claytonbrown/dokku,dokku/dokku,dokku/dokku,claytonbrown/dokku,dokku/dokku,claytonbrown/dokku,claytonbrown/dokku,claytonbrown/dokku,dokku/dokku,dokku/dokku,claytonbrown/dokku,dokku/dokku,dokku/dokku