dsync: Allow syncing same mail root dirs if indexes are different. Fixes dsyncing with storages that have no mail root dirs.
dsync: Allow syncing same mail root dirs if indexes are different.
Fixes dsyncing with storages that have no mail root dirs.

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