Update references to internal registry

[lberk]

Currently we use docker-registry.default.svc:5000/myproject/dumpy:latest
as well as image-registry.openshift-image-registry.svc:5000/myproject/dumpy:latest in the demo. This may change to image-registry.openshift-image-registry.svc:443 as noted in
openshift/cluster-image-registry-operator#259

Pending that merge we'll need to check and change that service hostname/port accordingly.