auth: passdb-blocking - Expose passdb_blocking_auth_worker_reply_parse Enables sharing code with passdb cache

Changed .h ifdef/defines to use <NAME>_H format. --HG-- branch : HEAD

Added auth_request_set_credentials() to modify credentials in passdb and implemented it for SQL passdb. Added passdb_need_set_credentials boolean to mechanisms to indicate that it's required (OTP will need it). Patch by Andrey Panin. --HG-- branch : HEAD

Forgot to add for blocking passdb/userdb workers.. --HG-- branch : HEAD