use stable release of docker registry

docker registry is currently evicting the glance/swift drivers to their
own plugins[1].  until their is a trusted build that includes glance
we should lock our default registry to one that works.

1 https://github.com/dmp42/docker-registry-driver-glance/

Change-Id: Ied1e6601d297b2a16cb609605491d6794dd16563
Merge "use stable release of docker registry"