Thanks Strahil, for your suggestions.
Actually, I was far beyond the pick-up point you describe, as the Gluster had all been
prepared and was operable, even the local VM was already running and accessible via the
GUI.
But I picked up your hint to try to continue with the scripted variant, and found that it
allowed me much better insight into what was going on.
I am a little worried, though, that it actually works a little differently from the
GUI-wizard variant, in any case the failures don't seem identical.
That would have implications in terms of test-automation, which I'd rather not have to
worry about.
In a separate test for the same operation on a separate set of hardware the installation
got significantly further, up to the point where the local VM had actually been moved onto
the Gluster storage and into the Cluster, but then failed a validation step at the very
end (while the VM is actually up and running, albeit only withe primary host and that
listed as "Unresponsive" while it's hosting the VM....)
I have opened a separate tickt for that...