If username lookup fails, return EX_USAGE instead of EX_TEMPFAIL because we haven't yet opened the log file.
If username lookup fails, return EX_USAGE instead of EX_TEMPFAIL because we
haven't yet opened the log file.

--HG--
branch : HEAD

jkerihuel/dovecot,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot,jkerihuel/dovecot