clientlog: add NTS-KE service

Instead of sharing the NTP rate limiting with NTS-KE, specify a new
service for NTS-KE and use it in the NTS-KE server.

Add ntsratelimit directive for configuration.

clientlog.h

@@ -33,6 +33,7 @@
 
 typedef enum {
   CLG_NTP = 0,
+  CLG_NTSKE,
   CLG_CMDMON,
 } CLG_Service;