Using admin@internal didn't work even if I set the permissions at vm level too...
It worked with my username (g.cecchi) that has SuperUser system privilege and also at VM level.
Is it yet necessary to have a user with SuperUser privilege at system level?
Tomorrow (today... ;-) I'm going to open a bugzilla to backport the feature.
Thanks again,
Gianluca

In the mean time I have opened this:
https://bugzilla.redhat.com/show_bug.cgi?id=1446474

Feel free to add any comment.

I would test your suggestions. It seems I already tried them with a "fenceuser" user, but they didn't work, but it was late in the night and possibly I missed something... ;-)

It has been very nice in less than a day to make a "poor man" P2V of a physical 2-nodes RHCS running cluster into oVirt and be able to reproduce and solve a problem we had during maintenance windows with clvmd not starting due to timeout issues.
And also with both production and intracluster networks of the virtual cluster based on OVN, without having to spend time waiting for network support, due to time constraints we had, as the next maintenance window will be today...

thanks to all

Gianluca