Track object version relationships

This adds another developer "helper trap" for inter-object version
dependencies. If an object that another object depends on is bumped
in version, this test will note the change and remind the developer
(or reviewer) that the parent needs a version bump and backport
rule added.

Change-Id: Ia81d034f850173401cd84a79b15ae0f7c80b9653
Adds get_instance_disk_info to compute drivers

Solves a live migration regression issue by adding the
get_instance_disk_info to the compute drivers that do not
have it already implemented.

The method is called by the compute manager.

Change-Id: If5cd9a6f5948c08ef5f1cba2eda31f1175709137
Closes-Bug: #1358719
Co-Authored-By: Ionut Balutoiu <ibalutoiu@cloudbasesolutions.com>
Merge "Track object version relationships"
Merge "Adds get_instance_disk_info to compute drivers"