[FLOC-965] Acceptance testing against rackspace.

This is based on #1010. The relative diff is [here](https://github.com/ClusterHQ/flocker/compare/acceptance-runner-FLOC-1070...rackspace-acceptance-FLOC-965).

The linking tests fail due to [FLOC-1084](https://clusterhq.atlassian.net/browse/FLOC-1084).


> The buildbot tutorial image builder will eventually upload to vagrantcloud for tagged releases, right? 

We will have something the will automate uploading to vagrantcloud (or somewhere else, maybe). That may even be buildbot. But I *don't* think it should be just be triggered off building of a tag, it should require some positive action to trigger.