Replace assertItemsEqual with assertCountEqual

Follow-up of [1]. After this patch was sent, two more assertItemsEqual
were added in [2]. This patch is fixing it.

[1] https://review.opendev.org/c/openstack/python-openstackclient/+/789410
[2] https://review.opendev.org/c/openstack/python-openstackclient/+/781637

Change-Id: Ic2276bd0ff0f5df76505f37d8994b3384d40e9a7

Author: amoralej

openstackclient/tests/unit/volume/v3/test_volume_message.py

@@ -198,7 +198,7 @@ def test_message_list(self):
             limit=None,
         )
         self.assertEqual(self.columns, columns)
-        self.assertItemsEqual(self.data, list(data))
+        self.assertCountEqual(self.data, list(data))
 
     def test_message_list_with_options(self):
         self.app.client_manager.volume.api_version = \
@@ -227,7 +227,7 @@ def test_message_list_with_options(self):
             limit=3,
         )
         self.assertEqual(self.columns, columns)
-        self.assertItemsEqual(self.data, list(data))
+        self.assertCountEqual(self.data, list(data))
 
     def test_message_list_pre_v33(self):
         self.app.client_manager.volume.api_version = \