Evacuated instance disk not deleted

Adds disk cleanup in case instance is not on shared storage.
Added new methods to compute.rpc and virt.driver interface to validate
that instance files located on shared storage on remote compute node.

Fixes bug 1156269

Change-Id: Ia4cc601d0d824ba04f595df96461cfa85ad3b90c
Merge "Evacuated instance disk not deleted"