When there's nothing to do to sync mbox, still commit index syncing instead of rollbacking because it may need to sync index internally.
When there's nothing to do to sync mbox, still commit index syncing instead
of rollbacking because it may need to sync index internally.

--HG--
branch : HEAD

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