power off VMs and cleanup only if configured && build was successful or unstable

[jeichler]

request from @pcfe
the VMs should only be shut down when

• configured in the job config
• and build was successful or unstable

right now I tend to put that in a subsequent job because of:

• limitations in the pipeline (status for stages and steps rather than just on the build itself)
• adds the possibility to cleanup and shutdown manually, via cron plus triggered by the pipeline job
• can be reused by all existing soe-ci-pipeline jobs probably

@pcfe: you might want to state your opinion on that first, before i start implementing this

[pcfe]

@jeichler as just discussed, subsequent job is exactly what I want.
Please go ahead and implement.