[FLOC-965] Acceptance testing against racksapce.

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).


So the summary for this file is basically "automate the steps we already knew about for setting up a machine (and which we documented in the install docs)" - which makes sense since we're trying to accomplish just what we had previously documented.

At some point it would be nice to be able to avoid duplicating this knowledge in these two places in these two forms.  If this were all shell script, I could imagine jumping through some hoops to share a single definition of that shell script between the acceptance tests and the documentation.  Since it's not, and since there's even some branching here (to support branches), that'd probably be tricky...

A step in that direction might be at least not duplicating the static pieces here - could the sphinx docs include some shell snippets that are shared by this (or a similar, non-Fabric :wink: version of this) code?  Does that even seem like a good idea?