Add a TestCase mixin for enabling caches in tests

By default, disable all caching in tests, to preserve test independence.
In order to enable caching, inherit from CacheSetupMixin, and specify
which cache configuration is needed.

[EV-32]

openedx/core/djangoapps/content/course_structures/api/v0/tests_api.py

@@ -16,6 +16,8 @@ class CourseStructureApiTests(ModuleStoreTestCase):
     """
     MOCK_CACHE = "openedx.core.djangoapps.content.course_structures.api.v0.api.cache"
 
+    ENABLED_CACHES = ['default', 'mongo_metadata_inheritance', 'loc_cache']
+
     def setUp(self):
         """
         Test setup