#620: logout requests should contain logoutRequest Parameter

This pull fixes issue #620
Ah, interesting! I think there's something wrong with my local git/dev environment. Changes seem to have a will of their own :)

But I was experimenting with unit tests to see if I could prove out this behvior, and so made the const here public so it can be compared with the outcome of a unit tests but eventually bailed. I'll revert this back.