Comment 3 for bug 1749201

https://code.launchpad.net/~chris.macnaughton/openstack-mojo-specs/upgrade-spec/+merge/337646 is a WIP set of helpers to iterate through upgrading all of the deployed units. As you can see, it looks a lot like the linked documentation, including reboots and, if coming from Trusty, updating to Systemd. At the end of that, the machine agent is back up, the machine shows Xenial, but no application agents come back up