Don't forget to remove the temporary directory in the config tests

When overriding the tear-down function, we must remember to call the
parent's function or we won't clean up the temporary directory for the
test.

test/test_config.py

@@ -46,6 +46,7 @@ def foreach_test_wrapper(key, name, lst):
 class ConfigTest(utils.RepoTestCase):
 
     def tearDown(self):
+        super(ConfigTest, self).tearDown()
         try:
             os.remove(CONFIG_FILENAME)
         except OSError: