FYI - https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=811481 :
When systemd is used, ovirt-guest-agent still doesn't start.  The
problem is that /var/log/ovirt-guest-agent owner is set to root:root, so
the daemon can't write to the directory and fails.  (The directory
ownership is fixed in init.d script but that is not executed with
systemd.)