reboot notification comes back after clear-notification action removes it

When the reboot of sysconfig in not required and the warning to reboot comes, then you can run clear-notification action to get rid of the warning and the status of machine becomes active. However, the warning message comes back after couple of minutes and the machine status is back to blocked.

Steps to recreate:
`juju deploy ubuntu`
`juju deploy sysconfig`
`juju add-relation sysconfig ubuntu`

The `juju status` will show blocked status on sysconfig unit with message 'update-grub and reboot required. Changes in: /etc/systemd/system.conf, /etc/default/grub.d/90-sysconfig.cfg'.

You can clear the above notification by running:
`juju run-action sysconfig/<unit> clear-notification --wait`
and the sysconfig status is active. However after couple of minutes, the status goes back to blocked with the same message. I believe the update-status hook runs and brings back the warning.