Making secondary disk of the instance available to the instance when it is in rescue mode.

Current Implementation of nova-rescue:
When a customer rescues his VM, the rescued VM has a rescue image as the primary file-system and
the secondary file-system would be the original VM's primary file-system .

Changes expected in nova-rescue implementation:
Along with the primary disk making secondary disk of the original VM available to the user in the rescued VM.

Reason for the changes:
If the user finds that his primary disk is not repairable after rescuing his VM, at this stage the user may want to copy data from his VM's primary and secondary disk before deleting the VM.In this case it would be better to make secondary disk of the original VM to be made available to the user in his rescued instance.