When there are multile USB devices, --host-device with bus.addr
can identify unique device, so we need to add bus/addr info to
XML rather than only vendor/product
If there is only one USB device with --host-device bus.addr,
adding bus/addr is no harm under the request of user.
When there are mutiple USB devices with identical vendorId and
productId, with --host-device <vendorId:productId>, virt-install
fails to specify one.
Currently the virt-install add the first node device with
these vendorId and productId.
This fix will throw out an error when argument to --host-device
can't specify unique node device.
For example:
virt-install ${other args} \
--host-device <vendorId:productId>
ERROR 15e1:2007 corresponds to multiple node devices