dependency on quay.io

[cgwalters]

(I believe) prior to b02a1ac kubernetes-ansible was just retrieving packages (or in the case of Atomic, pre-baked hosts) from the target distribution. Now we're pulling in a Docker image from quay.io.

Eventually I'd like to have k-a support air-gapped installation - and a step towards that is to limit external dependencies (and ideally, ensure secure retrieval via a whitelist of GPG keys or the like, but Docker is a bit far from that now).