This tests a number of things which have caused problems for us:
- resizing PVs and LV content
- handling GPT format disks
- using qcow2 as a target disk format
- shrinking disk images
Note that the disk content is empty (not a real VM), but this is
adequate since all we want to test are the operations and calculations
done by virt-resize. We are not interested here in whether e2fsprogs
and LVM actually works.