trivial: tests: add failure context to flakey assertion

An object server unit test was seen to fail returning a 409 when a 204
was expected. I cannot see the bug, so this patch adds some failure
context to add illumination if/when it fails again.

Change-Id: I45327cb5a56a87b8f6b9e971232fdce3b3f4bcb8
Related-Bug: #2131684
Signed-off-by: Alistair Coles <alistairncoles@gmail.com>

test/unit/obj/test_server.py

@@ -5614,7 +5614,8 @@ class TestObjectController(BaseTestCase):
                                 environ={'REQUEST_METHOD': 'DELETE'},
                                 headers={'X-Timestamp': timestamp.internal})
             resp = req.get_response(self.object_controller)
-            self.assertEqual(resp.status_int, 204)
+            self.assertEqual(resp.status_int, 204,
+                             (start, orig_timestamp, timestamp))
             objfile = os.path.join(
                 self.testdir, 'sda1',
                 storage_directory(diskfile.get_data_dir(POLICIES[0]), 'p',