dsync: Minor fix to deciding when to use GUIDs vs. header hashes.
dsync: Minor fix to deciding when to use GUIDs vs. header hashes.

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