Make attach_volume use **kwargs

As we discussed on
http://lists.openstack.org/pipermail/openstack-dev/2015-July/068864.html
All http POST/PUT methods need to contain **kwargs as their arguments.
This patch makes attach_volume use **kwargs.

Partially implements blueprint consistent-service-method-names

Change-Id: Ibc7f5c80755876318e1f5c7f7548276f315467c6
diff --git a/tempest/scenario/test_stamp_pattern.py b/tempest/scenario/test_stamp_pattern.py
index c1d9a1b..8b5a595 100644
--- a/tempest/scenario/test_stamp_pattern.py
+++ b/tempest/scenario/test_stamp_pattern.py
@@ -104,7 +104,7 @@
 
     def _attach_volume(self, server, volume):
         attached_volume = self.servers_client.attach_volume(
-            server['id'], volume['id'], device='/dev/%s'
+            server['id'], volumeId=volume['id'], device='/dev/%s'
             % CONF.compute.volume_device_name)
         self.assertEqual(volume['id'], attached_volume['id'])
         self._wait_for_volume_status(attached_volume, 'in-use')