Fix test settings

We can now run Tuskar UI tests from Horizon:

    ./tools/with_venv.sh ./manage.py test tuskar_ui --settings tuskar_ui.test.settings

Change-Id: I4900551a061d9714040f9f9a0972228b0ca218f6
Signed-off-by: Tomas Sedovic <tsedovic@redhat.com>
Merge "Fix test settings"