HTTP 500 Server error while creating an instance with a non existent network port parameter

Using Quantum as the network service, boot an instance and pass a non existent port
in the network parameter list.

Nova API Expected Error: 400 BadRequest
Actual Error: 500 Server Error

Though Quantum Client returns Status: 404, Nova API returns Status: 500

API Log snip:

2013-06-27 06:45:07.528 TRACE nova.api.openstack QuantumClientException: Port ca476808-bfa1-42c0-da1c-301973456e78 could not be found on network None
2013-06-27 06:45:07.528 TRACE nova.api.openstack
2013-06-27 06:45:07.537 INFO nova.api.openstack [req-a73d95ff-3235-4221-9ccc-ab478b84fc0e demo demo] http://10.2.3.102:8774/v2/a764d297000a47188db8dc1b5490d882/servers returned with HTTP 500
2013-06-27 06:45:07.538 DEBUG nova.api.openstack.wsgi [req-a73d95ff-3235-4221-9ccc-ab478b84fc0e demo demo] Returning 500 to user: The server has either erred or is incapable of performing the requested operation. from (pid=23318) __call__ /opt/stack/nova/nova/api/openstack/wsgi.py:1182
2013-06-27 06:45:07.539 INFO nova.osapi_compute.wsgi.server [req-a73d95ff-3235-4221-9ccc-ab478b84fc0e demo demo] 10.2.3.243 "POST /v2/a764d297000a47188db8dc1b5490d882/servers HTTP/1.1" status: 500 len: 359 time: 0.2387700

Affects: Nova trunk commit 9900e0549118e76df0ee47c68b76a1bc5ed1bd59