Testlab + Docker Registry with IPFS Storage Driver

@hsanjuan has made a lovely IPFS storage driver for the Docker registry here...

https://github.com/docker/distribution/pull/2906

I have built it from scratch and tested it locally on my iMac, and it seems to be working!

I think it would be great to build a Testlab scenario that set up more than one Docker install and more than one IPFS-enabled Docker registry, and do an end-to-end test:

1. on node 1, create a Docker image from a Dockerfile
2. push to a Docker registry running locally on node 1
3. on node 2, pull the image from a different Docker registry, running locally on node 2, which should fetch the data using IPFS from the registry on node 1