Fix to mailbox_dir_name handling. (Broke mbox .subscriptions filtering)
Fix to mailbox_dir_name handling. (Broke mbox .subscriptions filtering)

LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot