[MSGINA] Simplify the auto logon code path

[MSGINA] Simplify the auto logon code path

- Get rid of DoAutoLogon() and the AutoLogonState variable.
- Handle the auto logon in the normal logon code path instead.
- Set bAutoAdminLogon to FALSE on a successful login. This will prevent another automatic logon after a logoff.
- The IgnoreShiftOverride feature got lost by this change but I will add it again.