BecomeAnyAccountLoginServlet was the last user of
AccountAccess.byPreferredEmail. Instead of going to ReviewDb to lookup
accounts by preferred email, it's now doing a lookup from the account
index.
This is a preparation for migrating the accounts to NoteDb, because then
we can no longer lookup accounts by prefered email from ReviewDb.
Change-Id: I371f5791455435faf47764c684377304ebf02ff0
Signed-off-by: Edwin Kempin <ekempin@google.com>
8562864736