[ticket/12310] Don't autocomplete SMTP user/pass on install

PHPBB3-12310
Merge remote-tracking branch 'marshalrusty/ticket/12310' into develop-olympus

* marshalrusty/ticket/12310:
  [ticket/12310] Don't autocomplete SMTP user/pass on install
Merge branch 'develop-olympus' into develop-ascraeus

* develop-olympus:
  [ticket/12310] Don't autocomplete SMTP user/pass on install