openldap: Enable argon2 hash support by default
openldap: Enable argon2 hash support by default

argon2 is the recommended password hashing function, and the module is
included with OpenLDAP contrib.

This change enables argon2 hashes by default in our OpenLDAP package.

The install command for argon2 needs to be install-lib, as it otherwise
tries to install manpages to /usr, which fails.

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