This is our first attempt at running nodepool from docker, consider it
experimental. The idea here, is you now have the option of using the
official docker images from https://hub.docker.com/u/zuul for nodepool.
Users themself will be required to manage / configure docker, this role
only installs / configures / starts nodepool.
Change-Id: I2f3aa301e626a7b09ff129a21a188cee06e31f18
Signed-off-by: Paul Belanger <pabelanger@redhat.com>