Add unit tests to mapping_purge
Add unit tests to mapping_purge

This adds unit tests to mapping_purge.

Change-Id: I01a814f03e83911461168f4dac74202b6f0537d8
Closes-Bug: 1645568

openstack/keystone,openstack/keystone,mahak/keystone,mahak/keystone,openstack/keystone,mahak/keystone