rpm-ostree/notifier: Setup a watcher to trigger reboot check & fix update/reboot notification logic

rpm-ostree/notifier: Fix update/reboot notification logic

Only notify when there is an uninstalled update available and not in all cases. When we find a valid deployment for the updated version, we only need to notify to reboot.

---

rpm-ostree/notifier: Setup a watcher to trigger reboot check

To make sure that the notifier rechecks if a reboot is needed, we need to watch for changes made to ostree deployments.

To avoid triggerring the check mutiple times or while the rpm-ostree transaction is still running, we add a 10 second delay.