journal: don't try to reuse already calculated hash between files with keyed hash feature

When suppressing duplicate fields between files we so far tried to reuse
the already known hash value of the data fields between files. This was
fine as long as we used the same hash function everywhere. However,
since addition of the keyed hash feature for journal files this doesn't
work anymore, since the hashes will be different for different files.

Fixes: #19172