sriov hook: allow VFs with nonzero pci domain

This patch is the smallest change needed to expose a host nic with non-zero pci
domain to a guest.

The hook does a questionable detour via libvirt in order to extract the pci
address of the specified nic. This begs for simplification in a follow up patch.

Bug-Url: https://bugzilla.redhat.com/1092425
Change-Id: Ie2b75134a7f6bdb10f8d808b4dcda6856befe705
Signed-off-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/28162
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Marina Kalinin <marinamku@gmail.com>