Add ruby-libvirt to rpm-reqs

ruby-libvirt will be used to query libvirt for fence_virsh data

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>
Add custom facts for node.uuid, node.virsh_name

These facts will show virsh domain uuid & name for fence_virsh etc, if virtual;
otherwise will show system uuid (dmi.system.uuid), if any.

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>