Comment 2 for bug 1193113

The real solution here is to completely disregard the passed in device name when running libvirt/KVM as it cannot honor it. The API option is there only for hypervisors that support it such as Xen.

Roughly this can be done by the following steps:

1) Exposing a way for drivers to generate device names - much like is done now when booting (but not when attaching volumes to running instances for which we use a general helper method compute_utils.get_device_name_for_instance)
2) Make libvirt disregard what is passed into the new method and simply use it's own assignment methods. Fall back on the utils method in the other driver's implementations (much like is done when booting)