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

@@ -325,7 +325,7 @@ class TokenTests(object):
 
     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.assertDictEquals(data_ref, data)

tests/test_backend_memcache.py

@@ -42,7 +42,7 @@ class MemcacheClient(object):
         """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: