Clarify which images should be tested in DR builds

It should be clarified which images should be tested (including their sha hashes) as part of DR testing.

A canonical list of images should be part of the hand-off.

I assume there should only be two images:

• Karaf
• Java

Both of which should be usable for both S2I and fabric workflows.

(+ API registry/apiman, fabric8 console)