Instead of just using an image from a pre-defined url, the base image is
looked for in imagesdir, and the latest image of the right type is
selected.
imageurl can be used to override the image discovery, if force_imageurl
is set to True (False by default).
Before we actually can specify the required image's release/flavor/arch
in formula, temporary config options were added.
.
The config file and config_defaults should be kept in sync, can you please put the default URL here as well?