Added multi_db=True to test cases that access the 'other' db connection.

Fixed a failure in the context processors tests when running in
reverse on MySQL due to an extra query after refs #27683.

tests/migrations/test_base.py

@@ -18,6 +18,7 @@ class MigrationTestBase(TransactionTestCase):
     """
 
     available_apps = ["migrations"]
+    multi_db = True
 
     def tearDown(self):
         # Reset applied-migrations state.

tests/migrations/test_loader.py

@@ -11,6 +11,7 @@ class RecorderTests(TestCase):
     """
     Tests recording migrations as applied or not.
     """
+    multi_db = True
 
     def test_apply(self):
         """