mbox: When skipping subscriptions file, use the configured filename instead of hardcoded one.
mbox: When skipping subscriptions file, use the configured filename instead of hardcoded one.

--HG--
branch : HEAD

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