- Enable instantiated services (boo#1184165)

- Prepare instantiated service/timer support but not enable it:
This seems to fail due to missing systemd support right now.
So the only option at the moment is to copy the timer and unit
file for a 2nd instance. Mark all files as part of dehydrated.target

- Remove support for /etc/dehydrated/postrun-hooks.d/ directly in
dehydrated.service:
systemctl enable dehydrated-postrun-hooks.service
to restore this functionality
- Run dehydrated as dehydrated user again