Fix autodiscover when attempted with Exchange 2003 server

* Make sure 403 error in autodiscover isn't treated as an auth error
  (401 is used for that)
* Make non-auth errors in autodiscover fail silently (and move user
  to manual setup)

Bug: 2374302
Change-Id: I4699bff70cf5ec4a513e6443e4817543c2ab2cef
1 file changed