Add back necessary import.

Unit tests are failing because an import of glance/common/config.py was removed.
When it is imported it registers a few common cfg opts that otherwise would not
be registered. If this doesn't happen then unittests will fail since they expect
those opts.

Change-Id: Ib90c0af3d935243fd0aa8487131305f6843c1330

glance/tests/utils.py

@@ -28,6 +28,8 @@
 
 import nose.plugins.skip
 
+# NOTE(ameade): this import is necessary so that common cfg opts are registered
+from glance.common import config
 from glance.common import utils
 from glance.common import wsgi
 from glance import context