Do not rely on dogpile internals for mocks

Nova tests are broken under dogpile.cache===0.6.3 because of
https://bitbucket.org/zzzeek/dogpile.cache/commits/7f81a5ab304e9fe1a279168ee5f68d9077edb512

We need to fix the following tests to make sure we don't rely on
the arguments or order of arguments.
nova.tests.unit.test_cache.TestOsloCache.test_get_memcached_client

We can remove the following test as there is nothing much left
of actual value
nova.tests.unit.test_cache.TestOsloCache.test_get_client

Change-Id: I6fc342db2abb365d9e791b2f53701627d2a2beed

nova/tests/unit/test_cache.py

@@ -28,33 +28,6 @@ def test_get_default_cache_region_default_expiration_time(self):
         self.assertEqual(600, region.expiration_time)
         self.assertIsNotNone(region)
 
-    @mock.patch('dogpile.cache.region.CacheRegion.configure')
-    def test_get_client(self, mock_cacheregion):
-        self.assertIsNotNone(
-                cache_utils.get_client(expiration_time=60))
-
-        self.flags(group='cache', enabled=True)
-        self.assertIsNotNone(
-                cache_utils.get_client(expiration_time=60))
-
-        self.flags(group='cache', enabled=False)
-        client = cache_utils.get_client(expiration_time=60)
-        self.assertIsNotNone(client.region)
-
-        mock_cacheregion.assert_has_calls(
-                [mock.call('oslo_cache.dict',
-                           arguments={'expiration_time': 60},
-                           expiration_time=60),
-                 mock.call('dogpile.cache.null',
-                           _config_argument_dict=mock.ANY,
-                           _config_prefix='cache.oslo.arguments.',
-                           expiration_time=60,
-                           wrap=None),
-                 mock.call('oslo_cache.dict',
-                           arguments={'expiration_time': 60},
-                           expiration_time=60)],
-        )
-
     @mock.patch('dogpile.cache.region.CacheRegion.configure')
     def test_get_custom_cache_region(self, mock_cacheregion):
         self.assertRaises(RuntimeError,
@@ -82,9 +55,5 @@ def test_get_memcached_client(self, mock_cacheregion):
         self.assertIsNotNone(
                 cache_utils.get_memcached_client(expiration_time=60))
 
-        mock_cacheregion.assert_has_calls(
-                [mock.call('dogpile.cache.null',
-                           _config_argument_dict=mock.ANY,
-                           _config_prefix='cache.oslo.arguments.',
-                           expiration_time=60, wrap=None)]
-        )
+        methods_called = [a[0] for n, a, k in mock_cacheregion.mock_calls]
+        self.assertEqual(['dogpile.cache.null'], methods_called)