Code review comment for ~smoser/cloud-init:bug/1636912-systemd-cleanup

We should sync/link with a systemd but requiring systemd-networkd.service to drop After=dbus.service ... nto sure if https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1636912 covers that on the systemd side, without that, networkd/netplan enabled instances will break if they want to mount things early (like in Azure).