Virtuozzo hypervisor reports itself as 'vz' hypervisor, and it
was supported as libvirt virt type since Kilo. Let's expand
image metadata so that it will possible to filter out compute nodes,
which don't support images requiring hypervisor_type=vz
Lite-Spec-Id: I6ba0fcf670aecddde95cfdc6850cdb751dec2058
Change-Id: I51afacf83655107a6c4e4c226623fa360bdafca2