Refactor: Abstract columns out in TestFlavorList to avoid redundant code.
Refactor: Abstract columns out in TestFlavorList to avoid redundant code.

The columns has been set in each test case of TestFlavorList, which is not
necessary. This patch abstract it out and remove all redundant code.

Change-Id: Ideb2872f073755ac251bd603fd906410ea86c4ef
Implements: blueprint improve-flavor-unit-tes

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