Description of problem: Customers have the need to attach ISO to an instance that is already running. Currently there seems to only be possible to attach volume as type cdrom at boot time: https://access.redhat.com/solutions/1225473
Having this feature would allow customers to attach volumes containing iso image as type cdrom so they can install apps on windows vm and such via the iso.
So stable device rescue is what we really need here, the current behaviour of using the disk_bus of the original image or default in nova.conf is enough in the general volume-attach use-case.
*** This bug has been marked as a duplicate of bug 1449607 ***