Periodically rebuild container images

I'm picking up Yetus for a new repo in HBase and while I sit here waiting on my own image to build, I realised that Yetus images are stale. Starting from `yetus-base:0.14.1`, I have loads of packages to update. Since we expect users to be pulling these images directly, I think we should be explicitly calling `apt-get update && apt-get upgrade` and rebuild on a timer. I propose a weekly cadence, but almost anything will do.