After spending another couple of hours trying to track down the problem, I have found that
the "lost connection" seems due to KVM shutting down, because it cannot find the
certificates for the Spice and VNC connections in /etc/pki/vdsm/*, where
'ovirt-hosted-engine-cleanup' deleted them.
So now I wonder: Who is supposed to (re-)generated them afterwards?
Assuming that it was a much earlier step I proceeded to completely undo the deployment,
get rid of the Gluster setup etc. and start from the very beginning, only to find that
that didn't change a thing: It still missed those certificates....
...while something or someone *did* generated them when I tried a distinct and new set of
nodes for counter-testing..
That setup failed with an Ansible error (reported separately), but I have now grown afraid
of using 'ovirt-hosted-engine-cleanup' when I don't know how to get the
ciphers/keys for /etc/pki/vsdm/{spice|vnc} regenerated...
Can anyone shed some light into this darkness?