Unfortunately I could not find anything else that would indicate why the
host<->hosted-engine network is broken on the 4.5 oVirt.
I did attempt to get a reference installation (the oVirt Node
installation,
https://resources.ovirt.org/pub/ovirt-4.5/iso/ovirt-node-ng-installer/ovi...)
in order to do some comparative investigation. But unfortunately the
node installation is apparently also broken, albeit due a different bug
where the hosted-engine installation fails on identifying the LVM disks
it itself has set up. The node-installation was done on a Dell R740 with
plenty of disk so the HW configuration should not have been an issue.
Poltsi