Specify old mongo modulestore.

Testing migration from old mongo to split.

cms/djangoapps/contentstore/management/commands/tests/test_migrate_to_split.py

@@ -60,7 +60,7 @@ class TestMigrateToSplit(ModuleStoreTestCase):
 
     def setUp(self):
         super(TestMigrateToSplit, self).setUp(create_user=True)
-        self.course = CourseFactory()
+        self.course = CourseFactory(default_store=ModuleStoreEnum.Type.mongo)
 
     def test_user_email(self):
         """