nvp plugin does not handle 501 errors from NVP correctly

[Armando Migliaccio]

When calling non-existents NVP methods the server fails with:

2013-08-22 11:47:10.798 23678 TRACE NeutronPlugin AttributeError: 'NoneType' object has no attribute 'get'

This prevents proper cleanup

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/43347

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/43347
Committed: http://github.com/openstack/neutron/commit/0d2402b3fe8109160515f9b00dcdce3c35b8584e
Submitter: Jenkins
Branch: master

commit 0d2402b3fe8109160515f9b00dcdce3c35b8584e
Author: armando-migliaccio <email address hidden>
Date: Thu Aug 22 13:12:15 2013 -0700

    Deal with 501 errors from NVP correctly

    This is done by adding the error code to the exception
    handlers dictionary as done for other error codes.

    Fixes bug #1215583

    Change-Id: Ic876c6bccaf94cae626dfc908c4a34dfbcead406