[r=wallyworld] Container provisioners are not started until needed. The machine agent established what container types are supported on a given host and starts watchers which trigger when the first container of that type is requested. At that point, the provisoner is started.
This is the first in a series of changes which will also need the container dependencies be installed on an as required basis and other work done to improve container provisioning.
https://codereview.appspot.com/25040043/