Ticket 47427 - Overflow in nsslapd-disk-monitoring-threshold
    
    Bug Description:  The threshold setting was being stored as an "int" instead
                      of a PRUint64.  Config setting validation was also incomplete.
    
    Fix Description:  Changed the data type to PRUint64 from int, and improved the config
                      validation, and logging.
    
    https://fedorahosted.org/389/ticket/47427
    
    Reviewed by: richm & nhosoi(Thanks!!)