Option to "Login or register" when logged out of trusted consumer is confusing

[Stuart Metcalfe]

When logging out of a trusted site which implements our return_to argument, we display a link on the page to "Return to ..." which returns the user to the consumer site, but we also display the menu option to "Login or register" which logs the user back in to SSO. We should hide the top menu item on the logout page when the site users our return_to argument. If it makes the implementation less complicated, we could remove it from all logout pages as long as we add a "Return to Ubuntu SSO" link on the main page for normal logouts.