Comment 12 for bug 1442308

I'm quite certain I have a fix for this now, but I want to check with ericsnow to do some sanity checking before committing.

The short version is that we need to alter our cloud-config to properly use systemd to halt the container once cloud-init completes.

There were a couple of issues with the current config, but basically the unit file and its handling should change to:
1 - Include an [Install] section, even if this is a transient service.
2 - Not specify "Conflicts" when we want to stop after some other service completes. Using "Conflicts" will actually kill the service we're trying to run after if we start while it is still running.
3 - Change the "After" to be the cloud-config.target, rather than cloud-final(.service). See the cloud-config.target file for more info: https://github.com/stackforge/cloud-init/blob/master/inits/systemd/cloud-config.target
4 - After we enable the juju-template-restart service, we need to explicitly start it. But since we've added the cloud-config.target, we won't halt the system until after cloud-init completes.

After making the modifications above, I was able to deploy a trivial vivid charm successfully. I will get the code changes in tomorrow once I've chatted with Eric.

Basically, the issue is that we want to use systemd to start a service that will halt the container once cloud-init completes. As part of this service, we want it to remove itself such that other containers started from the template we're creating don't just halt once they start up.