[trivial] use systemctl for service management in Ubuntu
[trivial] use systemctl for service management in Ubuntu

service command is a wrapper for SystemV init scripts.
It's still working, but usage of systemd (systemctl) is more common since Ubuntu 16.04.

Change-Id: I59db9bf29696a1e64cdde322df29ec1a827d7e84

openstack/horizon,NeCTAR-RC/horizon,NeCTAR-RC/horizon,NeCTAR-RC/horizon,ChameleonCloud/horizon,ChameleonCloud/horizon,ChameleonCloud/horizon,NeCTAR-RC/horizon,ChameleonCloud/horizon,openstack/horizon,openstack/horizon,openstack/horizon