Rework stress to be more UnitTest like

[OpenStack Infra]

https://review.openstack.org/36752
commit 779047acb2afb3f36f4147e5f108f8e62c3d4ec8
Author: Walter A. Boring IV <email address hidden>
Date: Thu Jul 11 17:21:33 2013 -0700

    Rework stress to be more UnitTest like

    This patch reworks the stress test framework and
    the scripts to be a bit more flexible and to be
    like how unit tests are written. Instead of
    writing a module that contains functions, we now
    write an object that can implement a setUp and tearDown
    method. By default the object's 'run' method will be
    called by the driver.

    The setUp method will be called prior to calling run
    and tearDown will be called after run is stopped.

    DocImpact

    Change-Id: I39b8a1d38f70ddda4867126b58bb7053b45654d6