Meta server: fix Kerberos client authentication without user and group database, when only black and white lists are uses (this is the default mode for chunk server authentication). Implement an option to use user and group database with chunk server authentication. Fix authentication context's ssl psk context logic update by taking into the account the pending or current state of the Kerberos and x509 contexts depending if these were updated or not.
Kfsio library: fix client's authentication context update logic by taking into the account pending or current state of the Kerberos X509 contexts when updating PSK context depending if the previous two were updated or not.