add an option to check_enabled

[ChalyFlavour]

Some services are not ment to be enabled but may be monitored as well.
An option "check_enabled" (default: true) that would skip the "service.is_enabled()" case would be of great help

[helmo]

This is solved in a fork on https://github.com/Penbase/check-systemd-service

The specific commit is Penbase@1b55deb