Revert "Tests: Fail if oslo.versionedobjects issues Invalid UUID warnings"

This is currently causing unit test failures since
pymysql _show_warnings calls
    warnings.warn(err.Warning(*w[1:3]), stacklevel=4)
and this code assumes that the warnings are strings.

This reverts commit ed6d50bed6.

Change-Id: I81dc6f1ac5855b21c10572797fd45a6b38641112
(cherry picked from commit cc6c5b1086)

cinder/test.py

@@ -228,7 +228,6 @@ class TestCase(testtools.TestCase):
                              group='oslo_policy')
 
         self._disable_osprofiler()
-        self._disallow_invalid_uuids()
 
         # NOTE(geguileo): This is required because common get_by_id method in
         # cinder.db.sqlalchemy.api caches get methods and if we use a mocked
@@ -257,17 +256,6 @@ class TestCase(testtools.TestCase):
                        return_value=mock_decorator)
         p.start()
 
-    def _disallow_invalid_uuids(self):
-        def catch_uuid_warning(message, *args, **kwargs):
-            ovo_message = "invalid UUID. Using UUIDFields with invalid UUIDs " \
-                          "is no longer supported"
-            if ovo_message in message:
-                raise AssertionError(message)
-
-        p = mock.patch("warnings.warn",
-                       side_effect=catch_uuid_warning)
-        p.start()
-
     def _common_cleanup(self):
         """Runs after each test method to tear down test environment."""