add new test for configuration show unmask
add new test for configuration show unmask

Change-Id: Ib85bfa627f4ddee9e017f148c86a6d7d640bfba4

BjoernT/python-openstackclient,openstack/python-openstackclient,redhat-openstack/python-openstackclient,dtroyer/python-openstackclient,openstack/python-openstackclient,redhat-openstack/python-openstackclient,dtroyer/python-openstackclient,BjoernT/python-openstackclient