[1.2.X] Fixed #15622 -- Clear content type cache to avoid problems with subsequence TransactionTestCases. Thanks to zyga for the report

Backport of r15867 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@15868 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/contenttypes/tests.py

@@ -22,6 +22,7 @@ class ContentTypesTests(TestCase):
     def tearDown(self):
         settings.DEBUG = self.old_DEBUG
         Site._meta.installed = self.old_Site_meta_installed
+        ContentType.objects.clear_cache()
 
     def test_lookup_cache(self):
         """