allow to clear extra routes in nvp

[Armando Migliaccio]

This was allowed since fix done in: https://review.openstack.org/#/c/17436/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/37820

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/37820
Committed: http://github.com/openstack/neutron/commit/0f129121a1c8331c702204cf95951444ae53ef9c
Submitter: Jenkins
Branch: master

commit 0f129121a1c8331c702204cf95951444ae53ef9c
Author: armando-migliaccio <email address hidden>
Date: Thu Jul 18 17:53:18 2013 -0700

    Allow to clear extra routes in NVP

    Since the neutron client can unset any attribute, ensure
    we can handle empty routes as a way to clear the extraroutes
    for the router.

    Fixes bug #1202890

    Change-Id: Ib240a42ba1075d9a410da904b3d3ae9e19b2d86e