Some containers require Zemke-Rhyne to provision credentials.

In the current state of the unit, the first pass applying the roles/paas-docker will have some failures for Etherpad and Cachet containers, as all isn't ready to query zr.

To zr work we need:

• a zr command
• a Phabricator container (and so a MySQL container)
• a front-end nginx to pass the request to the container

Plan is to ensure a sane order for Docker role:

1. We need nginx to be first, so HTTP access to containers work
2. Wrappers must be there before containers too, so we can use the zr command
3. Now it's time for containers in the following orders:
4. MySQL (required by Phabricator)
5. Phabricator (required by zr containers)
6. Other ones