Greenboot service monitor not to trigger failure if any service is disabled

[say-paul]

Current greenboot-service-monitor implementation validates the active state of the services irrespective if its enabled or not,
which causes unforced issue when user disables any service and put the same in the greenboot config to monitor.

Can be resolved by the following process:

service enabled? Yes -> service active? -> Yes -> boot success
                 No ->  boot success        No -> trigger redboot.target

[say-paul]

no persuing service monitor anymore