docker_restart_policy: no causes systemd units to not get created
and we use it in CI to disable restarts on services.

Introducing oneshot policy to not create systemd unit for oneshot
containers (those that are running bootstrap tasks, like db
bootstrap and don't need a systemd unit), but still create systemd
units for long lived containers but with Restart=No.

Change-Id: I9e0d656f19143ec2fcad7d6d345b2c9387551604