Read and write full 20 bytes/40 hex chars of SHA1 key hash,
instead of some abridged versions. See also
https://lists.debian.org/debian-devel/2016/08/msg00215.html

Change-Id: I741afc94ac7cf559880fe55ff02420723e13310d
Reviewed-on: https://gerrit.libreoffice.org/40027Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
Tested-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>