This patch refactors ensure-docker to use the new ensure-package-repostories
role which cleans up the codebase for it a lot. It also converges the
Debian and Ubuntu configuration as they were pretty much the same.
Also, it updates the Docker to the proper GPG key as while refactoring,
it was exposed that it was using the wrong key. Docker uses a different
key for Debian and RHEL based packaging.
Change-Id: Iad430c6a31be0750c1a0f50e12a26df230de9f4e