Make create_image 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 create_image **kwargs.

Partially implements blueprint consistent-service-method-names

Change-Id: I788c84aae52b34b165fdb220b0f6de1b555b6f22
diff --git a/tempest/scenario/manager.py b/tempest/scenario/manager.py
index e77d07c..5bff1b4 100644
--- a/tempest/scenario/manager.py
+++ b/tempest/scenario/manager.py
@@ -402,7 +402,7 @@
         if name is None:
             name = data_utils.rand_name('scenario-snapshot')
         LOG.debug("Creating a snapshot image for server: %s", server['name'])
-        image = _images_client.create_image(server['id'], name)
+        image = _images_client.create_image(server['id'], name=name)
         image_id = image.response['location'].split('images/')[1]
         _image_client.wait_for_image_status(image_id, 'active')
         self.addCleanup_with_wait(