Use testtools instead of unittest or unittest2.
Use testtools instead of unittest or unittest2.

As part of the move towards testr and parallel test running, we
start to use testtools and fixtures to make the test suite
resilient and more pedantic.

Part of blueprint grizzly-testtools

Change-Id: I90250de9fe21237db34f6a50b89b15863e270aa5

yamt/networking-ofagent-old3,budnyjj/ofagent,budnyjj/ofagent,yamt/networking-ofagent