I believe without the inclusion of a developer on this thread it makes sense not to work with a single host because if you're trying to test fencing (via the power management setup) then how the host will fence itself and validate it. This of course when testing with a single host.
I believe the option is labeled incorrectly on ovirt because it should not be called power management if you're performing fencing with it.
there should be a an explicit button or setup option for fencing and another one for power management things. this leads to confusing terms and this is one of the features that sometimes keep people from testing systems like ovirt and sticking with hyper-v or VMware where options are clearly described.
once again it makes no sense to me to test fencing with a single host on my environment. that's why I believe developers failed to document the fact that you need at least two host to test fencing.
I could be totally wrong but as I learn ovirt here I have never ever been able to test fencing with a single host, always with two or more hosts previously configured.