cinderclient service catalog lookup fails

If your auth system isn't adding the service_catalog in the request headers, you get an unhandled exception in cinderclient.

2012-09-10 14:44:55 INFO nova.api.openstack.wsgi [req-3ab60e8c-888d-4d63-b857-1de0db0e0ac8 account1 account1] POST http://localhost:8774/v1.1/account1/servers/5b92fa58-ab9c-4140-b841-64d0c41786c9/os-volume_attachments
2012-09-10 14:44:55 AUDIT nova.api.openstack.compute.contrib.volumes [req-3ab60e8c-888d-4d63-b857-1de0db0e0ac8 account1 account1] Attach volume d7f55869-e888-4e1a-94f3-561725a4def6 to instance 5b92fa58-ab9c-4140-b841-64d0c41786c9 at /dev/vdf
2012-09-10 14:44:55 DEBUG nova.openstack.common.rpc.amqp [-] Making asynchronous call on compute.nova ... from (pid=29457) multicall /opt/nova/nova/openstack/common/rpc/amqp.py:351
2012-09-10 14:44:55 DEBUG nova.openstack.common.rpc.amqp [-] MSG_ID is e1918d3455b94332b78b55b5eea4fa10 from (pid=29457) multicall /opt/nova/nova/openstack/common/rpc/amqp.py:354
2012-09-10 14:44:55 ERROR nova.api.openstack.wsgi [req-3ab60e8c-888d-4d63-b857-1de0db0e0ac8 account1 account1] Exception handling resource: 'NoneType' object is not iterable
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi Traceback (most recent call last):
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi File "/opt/nova/nova/api/openstack/wsgi.py", line 925, in _process_stack
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi action_result = self.dispatch(meth, request, action_args)
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi File "/opt/nova/nova/api/openstack/wsgi.py", line 1013, in dispatch
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi return method(req=request, **action_args)
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi File "/opt/nova/nova/api/openstack/compute/contrib/volumes.py", line 392, in create
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi volume_id, device)
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi File "/opt/nova/nova/compute/api.py", line 114, in wrapped
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi return func(self, context, target, *args, **kwargs)
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi File "/opt/nova/nova/compute/api.py", line 104, in inner
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi return function(self, context, instance, *args, **kwargs)
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi File "/opt/nova/nova/compute/api.py", line 1750, in attach_volume
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi context, instance['uuid'], device)
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi File "/usr/lib/python2.7/contextlib.py", line 24, in __exit__
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi self.gen.next()
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi File "/opt/nova/nova/compute/api.py", line 1742, in attach_volume
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi volume = self.volume_api.get(context, volume_id)
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi File "/opt/nova/nova/volume/cinder.py", line 135, in get
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi item = cinderclient(context).volumes.get(volume_id)
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi File "/opt/nova/nova/volume/cinder.py", line 59, in cinderclient
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi endpoint_type=endpoint_type)
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi File "/opt/python-cinderclient/cinderclient/service_catalog.py", line 53, in url_for
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi for service in catalog:
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi TypeError: 'NoneType' object is not iterable
2012-09-10 14:44:55 TRACE nova.api.openstack.wsgi
2012-09-10 14:44:55 INFO nova.api.openstack.wsgi [req-3ab60e8c-888d-4d63-b857-1de0db0e0ac8 account1 account1] http://localhost:8774/v1.1/account1/servers/5b92fa58-ab9c-4140-b841-64d0c41786c9/os-volume_attachments returned with HTTP 400
2012-09-10 14:44:55 INFO nova.osapi_compute.wsgi.server [req-3ab60e8c-888d-4d63-b857-1de0db0e0ac8 account1 account1] 127.0.0.1 - - [10/Sep/2012 14:44:55] "POST /v1.1/account1/servers/5b92fa58-ab9c-4140-b841-64d0c41786c9/os-volume_attachments HTTP/1.1" 400 338 0.274771

I'd actually prefer to be able to set the cinder endpoint via a flag for two reasons.

1) if you're using a reverse proxy, or another auth system, it may not be convenient or even make sense to add a copy of the service catalog to the request headers/context - the KeystoneContext middleware certainly seems to support the idea that it may not always be there. Plus, glance uses flags afaict, and that works ok.
2) There may be good reasons for the management endpoint that nova uses to talk to cinder to be different than the public endpoint, so the users catalog may not really help. (e.g. public endpoint has os-volume_actions ext disabled to prevent user calling detach directly without updating nova)

The attached patch also happens to support noauth just cause it was "right there"