Add waiting for image readiness (OTC)

Created by: garloff

After the image registration is completed, it might not yet be ready for use. (This is the case on OTC at least.) So do the following improvement:

• Do image registration in background, only wait for it to be visible in the img catalog in the upload script
• In the main script, before considering clusterapi deployment to be complete, wait for image to be ACTIVE This should both speed up things (higher paralellism) as well as ensuring that things are ready, even on OTC.