Add desktop notification for clr-service-restart

[puneetse]

When services need to be manually restarted after a system update, clr-service-restart provides a useful terminal/SSH MOTD notification.

I think it would also be a useful message to have as a desktop notification so graphical users know services should be restarted for an update to complete.

libnotify could be levered with notify-send so it works across multiple desktop environment.

Perhaps it can be added to this: https://github.com/clearlinux-pkgs/clr-service-restart/blob/master/0001-Motd-updating-script-for-clearlinux.patch