Revert "Implement ability for hg logins to try fallback regions just like local logins."

This approach does not work - it is taking place too far down the login process where really the region checking
could only be done when the hg map tiles are linked on the main map (messy and probably impossible) or possibly
when the final destination is fetched at the very first stage of teleport (which couldn't be done without a protocol
change to pass the agentID as well as the requested regionID)

This reverts commit 3d9b73c47a15cf00150ac80570fea88de8cecbdf.
minor: Make logging in GatekeeperService.LoginAgent() a bit more detailed so that we can distinguish between simultaneous logins