Modify notification_pref tests to avoid changes to module store

Calling the client root was causing the module store to be modified,
affecting test in other Django applications that rely on the default
state of the module store.

lms/djangoapps/notification_prefs/tests.py

@@ -20,11 +20,6 @@ from util.testing import UrlResetMixin
 class NotificationPrefViewTest(UrlResetMixin, TestCase):
     INITIALIZATION_VECTOR = "\x00" * 16
 
-    @classmethod
-    def setUpClass(cls):
-        # Make sure global state is set up appropriately
-        Client().get("/")
-
     @patch.dict("django.conf.settings.FEATURES", {"ENABLE_DISCUSSION_SERVICE": True})
     def setUp(self):
         super(NotificationPrefViewTest, self).setUp()