Add support for Swift Api Auth

I was using the deprecated SwiftClient and authentication against it by using the "swift" provider and "/auth" endpoint.
I was convinced I should use the new SwiftApi from labs to give feedback. However I cannot, because the labs requires keystone auth, which we have not set up. We authenticate directly against radosgw. Because this was possible in 1.7.1 SwiftClient, I consider this missing functionality in the SwiftApi labs.