Revert "Revert "Unit test for checking cross-version migrations compatibility""
Revert "Revert "Unit test for checking cross-version migrations compatibility""

This reverts commit c5a1b47bf9ef70a35231c4701c638a157d5dfe7a.

Based on the Newton summit, we need to restore this as a first step towards changing developer mindsets :)

Change-Id: I846ad6bc1a3144f51b538b71b6f4c8c9b1073f21

openstack/keystone,rajalokan/keystone,ilay09/keystone,mahak/keystone,cernops/keystone,openstack/keystone,mahak/keystone,ilay09/keystone,rajalokan/keystone,openstack/keystone,rajalokan/keystone,mahak/keystone,ilay09/keystone,cernops/keystone