[horde] Turning off Language Dialogue In Horde

[Bauer, Rich]

I want to turn off the language selection dialogue on the Horde login and
IMP login page and just force it to be English.

I followed the instructions found in several mailing list archives saying to
edit prefs.php and lock the language, however the dialogue still appears on
the login screens.

// user language
$_prefs['language'] = array(
    'value' => 'en_US',
    'locked' => true,
    'shared' => true,
    'type' => 'select',
    'desc' => _("Select your preferred language:"));

Is there something else that needs to be done ?