Comment 5 for bug 1729516

Modifying the pre/post-inst files I found that really virtlogd is just active by this sysv accident that is left.

For virtlockd as outlined it fails to enable at:
 $ deb-systemd-invoke start virtlockd.service
 virtlockd.service is a disabled or a static unit, not starting it.
virtlogd behaves the same way in regard to this command.

Well actually this should be correct I think.
The socket is enabled:
# systemctl status virtlockd.socket
● virtlockd.socket - Virtual machine lock manager socket
   Loaded: loaded (/lib/systemd/system/virtlockd.socket; enabled; vendor preset: enabled)
   Active: active (listening) since Mon 2017-11-06 14:22:48 UTC; 13min ago
   Listen: /var/run/libvirt/virtlockd-sock (Stream)

And the service is inactive (by being indirect) as it is an Also=virtlockd.socket
# systemctl status virtlockd.service
● virtlockd.service - Virtual machine lock manager
   Loaded: loaded (/lib/systemd/system/virtlockd.service; indirect; vendor preset: enabled)
   Active: inactive (dead)
     Docs: man:virtlockd(8)
           http://libvirt.org

I was able to activate it through that socket and this matches https://libvirt.org/locking-lockd.html#sanlock

All that said, I'll suggest that change to provide the defaults file correctly to Debian now.