Provide production configuration for the image registry operator

[russellb]

So far in dev-scripts, we have been manually configuring the image registry operator to use the emptyDir backend. This just makes it use local storage, and is not intended for any production use.

https://github.com/openshift-metal3/dev-scripts/blob/master/assets/templates/99_registry.yaml

In the following PR, I've proposed a patch to move this default into the image registry operator, so we can drop this manifest from dev-scripts and still have the cluster deploy cleanly.

openshift/cluster-image-registry-operator#332

Since emptyDir is not a production backend for the registry, install-scripts needs to immediately reconfigure it to use a PVC after OCS has been deployed and a PVC can be created.