nicira tests cleanup

[Armando Migliaccio]

Addressing reviewer's comment in:

https://review.openstack.org/#/c/34675/10/neutron/tests/unit/nicira/test_agent_scheduler.py

On a larger scale.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/38561

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/38561
Committed: http://github.com/openstack/neutron/commit/e08e959834ee2c0685bf594421216ebf58da2d2f
Submitter: Jenkins
Branch: master

commit e08e959834ee2c0685bf594421216ebf58da2d2f
Author: armando-migliaccio <email address hidden>
Date: Wed Jul 24 16:03:49 2013 -0700

    Clean-up in the unit tests for NVP plugin

    Simplify and reduce duplication in the unit test framework
    for the NVP plugin.

    Fixes bug 1204694

    Change-Id: Ia96e1c2386ac013c24a2c7716d0e97ea6fdcf5d1