You should be able to see the hosts from ovirt interface.
I was not able to add an auto-discovered hosts to ovirt it always trows
an
exception: Failed to add Host <UNKNOWN> (User: admin@internal). probably
it is a bug.
Did you add the oVirt provision plugin to Foreman? You probably need it for
this to work.
If you did then please submit a bug to oVirt bugzilla.
Thanks,
Barak