Specify old mongo modulestore.

Tests verify operation counts for old mongo. Should be extended to split in the future.

cms/djangoapps/contentstore/tests/test_course_listing.py

@@ -53,7 +53,8 @@ class TestCourseListing(ModuleStoreTestCase):
         course = CourseFactory.create(
             org=course_location.org,
             number=course_location.course,
-            run=course_location.run
+            run=course_location.run,
+            default_store=ModuleStoreEnum.Type.mongo
         )
 
         if user is not None: