qemu: hotplug: Assume QEMU_CAPS_DEVICE in qemuDomainAttachVirtioDiskDevice
qemu: hotplug: Assume QEMU_CAPS_DEVICE in qemuDomainAttachVirtioDiskDevice

After killing one of the conditionals it's now guaranteed to have
@drivealias populated when calling the monitor, so the code attempting
to cleanup can be simplified.

crobinso/libvirt,taget/libvirt,jardasgit/libvirt,eskultety/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,olafhering/libvirt,jardasgit/libvirt,datto/libvirt,datto/libvirt,jardasgit/libvirt,nertpinx/libvirt,jardasgit/libvirt,andreabolognani/libvirt,datto/libvirt,libvirt/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,eskultety/libvirt,taget/libvirt,andreabolognani/libvirt,libvirt/libvirt,eskultety/libvirt,zippy2/libvirt,zippy2/libvirt,jfehlig/libvirt,crobinso/libvirt,olafhering/libvirt,VenkatDatta/libvirt,jfehlig/libvirt,eskultety/libvirt,nertpinx/libvirt,zippy2/libvirt,crobinso/libvirt,olafhering/libvirt,libvirt/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt,taget/libvirt,nertpinx/libvirt,datto/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,olafhering/libvirt,taget/libvirt,jfehlig/libvirt,libvirt/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,zippy2/libvirt,eskultety/libvirt,datto/libvirt,taget/libvirt,crobinso/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt