Create a service for powering on vms

When using vms, kni-upi-lab had to change the default shutdown mode from restart to power off. This is causing a side problem, that when the vm is rebooted naturally, it's not really rebooting, but permanently powering off.
To solve that, kni-upi-lab runs some script in the background that powers on the automatically powered off vms. But this script can die, or can just be killed if the host is powered off.
It should be convenient to replace this script with a service, so it's run permanently . It can be created on prepare_manifests, and be destroyed on destroy_cluster, to keep the system clean.