This builds from the image-signatures-rest branch for
https://github.com/openshift/origin/pull/9181 .
Testing push, pull, streaming.
Does not test working with the other Docker registries built in
Dockerfile; I will leave that to the author of that code :)
Note that this relies on an internet connection for pulling from the
Docker Hub (which is incidentally tested by that); pushing to no Docker
Registry, neither local nor Hub, is tested by this.
The tests only run in a container because the (oc login) / (docker
login)-like code modifies files in a home directory; the new
SKOPEO_CONTAINER_TESTS environment variable should protect against
accidental non-container runs.
