Daemon group based on restart test

base on https://github.com/autotest/autotest-docker/pull/255
This seems a likey area for things to break if non-RH distro or ``docker.socket`` goes missing.  I haven't actually seen any problems with systemd triggering on ``docker.socket``.  Is this a real problem that needs to be fixed now, or can we just pretend ignorance?

Either way, if there is local disabling of pylint errors because avoiding the issue is unwieldy,  I'd like them to come with comments explaining why so us old-farts don't need to guess or try and remember :wink: