hyperv: ambiguous VM names will throw an error

hyperv: ambiguous VM names will throw an error

Since Hyper-V allows multiple VMs to be created with the same name,
some commands produce unpredictable results due to
hypervDomainLookupByName's WMI query selecting the wrong domain.

For example, this prevents `virsh dumpxml` from outputting XML for the
wrong domain.

Signed-off-by: Matt Coleman <matt@datto.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>