Clear caches between tests for ModuleStoreTestCase/SharedModuleStoreTestCase

Cached values were leaking across tests, causing difficult to debug errors,
particularly when using Config Models. As part of this work, certain tests
that had query counts that relied on those values being cached needed to
be adjusted up.

lms/djangoapps/course_structure_api/v0/tests.py

@@ -520,7 +520,7 @@ class CourseBlocksOrNavigationTestMixin(CourseDetailTestMixin, CourseViewTestsMi
         return 'course_structure_api:v0:' + self.block_navigation_view_type
 
     def test_get(self):
-        with check_mongo_calls(3):
+        with check_mongo_calls(4):
             response = super(CourseBlocksOrNavigationTestMixin, self).test_get()
 
         # verify root element