Ticket 47499 - if nsslapd-cachememsize set to the number larger than
                    the RAM available, should result in proper error message.
    
    Bug Description:  The server allows any value to be set for all the cache sizes.  If
                      this value is too large it will basically crash the server.
    
    Fix Description:  Do a value verification before allowing the change.  Report an
                      error 53 and a descriptive error string if the value is too large.
    
    https://fedorahosted.org/389/ticket/47499
    
    Reviewed by: nhosoi(Thanks!!)