Use FakeFlavor in TestFlavorUnset.
Use FakeFlavor in TestFlavorUnset.

Change-Id: Ifbd360db39d380efd9632300367b13283ac75f54
Implements: blueprint improve-flavor-unit-test

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