Check if the credentials used for minishift tests are working

[anjannath]

I suspect the xpaas add-on tests are failing due to wrong credentials for registry.redhat.io.

minishift-ci-jobs/minishift-ci-index.yaml

Lines 21 to 24 in 6368e07

	- username-password-separated:
	credential-id: 3633c494-f063-4ae0-963d-9c0f975597ae
	username: RH_REGISTRY_USERNAME
	password: RH_REGISTRY_PASSWORD