REP-1271 Implement Delegation in Client AuthN

So the only thing I don't like about this change is that the message is not very descriptive. Unfortunately, to provide a more descriptive message I would have to spend a fair amount of time refactoring the authentication filter. Options there include returning an object that includes a message, using ThreadLocal, or refactoring the code to be less distributed so that setting the header alongside the status code makes sense.

I also did not run the system test suite locally, so some of those may not pass. Let's find out!
Check out the OpenStackAuthenticationHeaderManager class. When I construct the delegation header, I use whatever status code is returned by filterDirector.getResponseStatusCode(). Since we set that value all over the place, this seemed to be the easiest way to consolidate the logic.