Add device bus and type to virt attach_volume call

These two can be passed in the API when booting instances, and this
patch adds them to the relevant virt driver calls, so that they can be
passed when attaching volumes.

Part of the blueprint: use-new-bdm-format-in-attach

Change-Id: Ia961cae2b4bb3554f8d360c67144eb135df5528f