Modify vm_vdi_cleaner to handle `-orig`.
Modify vm_vdi_cleaner to handle `-orig`.

Also modifies the code to better handle various race conditions.

Fixes bug 1000359

Change-Id: I421b5827330da550810598cfbacc5bb679b477c7

openstack-dev/hacking,hyakuhei/cleantox,zancas/hacking,zancas/hacking,emonty/oslo-hacking,emonty/oslo-hacking,hyakuhei/cleantox,openstack-dev/hacking