qga-win: handle multi-disk volumes

qga-win: handle multi-disk volumes

Probe the volume for disk extents and return list of all disks.
Originally only first disk of composite volume was returned.

Note that the patch changes get_pci_info() from one state of brokenness
into a different state of brokenness. In other words it still does not do
what it's supposed to do (see comment in code). If anyone knows how to
fix it, please step in.

Signed-off-by: Tomáš Golembiovský <tgolembi@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>