Fix expired token tests

Fixes bug #983800

The expiration timestamps are expressed in UTC time, so ensure:

 1) The timestamp of the token created by the test is UTC time (i.e.
    utcnow() vs now())

 2) The expiration check in the dummy memcache client properly
    accounts for UTC (i.e. utctimetuple() vs timetuple())

Change-Id: Ie7356456f79ab5a8070a79771bb7d210b1cedd47

tests/test_backend.py

@@ -326,7 +326,7 @@ def test_token_crud(self):
 
     def test_expired_token(self):
         token_id = uuid.uuid4().hex
-        expire_time = datetime.datetime.now() - datetime.timedelta(minutes=1)
+        expire_time = datetime.datetime.utcnow() - datetime.timedelta(minutes=1)
         data = {'id': token_id, 'a': 'b', 'expires': expire_time}
         data_ref = self.token_api.create_token(token_id, data)
         self.assertDictEqual(data_ref, data)

tests/test_backend_memcache.py

@@ -42,7 +42,7 @@ def get(self, key):
         """Retrieves the value for a key or None."""
         self.check_key(key)
         obj = self.cache.get(key)
-        now = time.mktime(datetime.datetime.utcnow().timetuple())
+        now = time.mktime(datetime.datetime.utcnow().utctimetuple())
         if obj and (obj[1] == 0 or obj[1] > now):
             return obj[0]
         else: