KB Pillar - Ensure requested salted checksum isn't overwriting

Currently, when running GetChecksum on the KB Pillar, if the checksum returned using the given algorithm + salt is null, i.e. it's not saved in the Database or the in Memory File object, then it will recalculate the checksum with the given algorithm and salt.

We need to ensure that this newly computed checksum does not overwrite the checksum that is stored in the database. It also doesn't need to be saved to the database, as any salted checksum should not be reused, because that defeats the purpose of a salted checksum.