When the proxy id is set, this bus takes the name "id.0" which is expected
to be the virtio-device's first bus.

So force this name to "virtio-bus" as it is an internal bus.
Signed-off-by: NKONRAD Frederic <fred.konrad@greensocs.com>
Tested-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Message-id: 1367330931-12994-2-git-send-email-fred.konrad@greensocs.com
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>