Adding Networking test fixture

* Networking fixture with cleanUp methods for networks, subnets, ports
* delete and failed lists to handle the keep_resources and keep_failed_resources_on_failure flags
* using addClassCleanup so no need for a tearDown method (this will call the cleanUp method if a setUp fails)
* compute integration fixture

Change-Id: Ie0799bc9e2234b0c3bcf67e3422664db3b9dcd86