Repair virt.init KVM image distribution after disk_profile

This is needed to unblock testing virt.init on KVM.

This should be reviewed by @holmboe to make sure I didn't misunderstand the disk profile stuff. 

- use disk_profile instead of get_image_info
- repair mismatch between file cache copy, and DOM XML
- embed pool info in disk_profile.  Seems consistent with the profile
  goals

- added a return value of vm_info to init (it should return something
  useful, right!)