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/api/compute/volumes/test_attach_volume.py b/tempest/api/compute/volumes/test_attach_volume.py
index 8e4278a..6496854 100644
--- a/tempest/api/compute/volumes/test_attach_volume.py
+++ b/tempest/api/compute/volumes/test_attach_volume.py
@@ -83,7 +83,7 @@
         # Attach the volume to the server
         self.attachment = self.servers_client.attach_volume(
             self.server['id'],
-            self.volume['id'],
+            volumeId=self.volume['id'],
             device='/dev/%s' % self.device)
         self.volumes_client.wait_for_volume_status(self.volume['id'], 'in-use')