Remove dead code for showing login form to logged-in users

Since d0439af8, trying to view the login form while logged-in just
redirects to the 'returnto' address (or the main page), so this code
is unreachable.

Change-Id: I9ab8ab83172063d8facc491042832513d27f876b
Merge "Remove dead code for showing login form to logged-in users"