Regulate and add frame and byte count for CGNAT syslog messages

You can enable or disable the display of the CGNAT syslog message in certain deployment scenarios. When you configure the disable-session-open-syslog statement at the [edit services service-set service-set-name service-set-options] hierarchy: 

•  The JSERVICES_SESSION_OPEN logs are disabled and are no longer generated for the incoming sessions. 
•  The JSERVICES_SESSION_CLOSE logs, which are generated after the incoming sessions are closed, are printed with byte and packet count for the packets received and sent as part of the same session.