log more changes made by chronyc commands

Log important changes from chronyc for auditing purposes.

Add log messages for:
- loaded symmetric keys and server NTS keys (logged also on start)
- modified maxupdateskew and makestep
- enabled/disabled local reference mode (logged also on start)
- reset time smoothing (logged also on clock steps)
- reset sources

keys.c

@@ -255,6 +255,8 @@ KEY_Reload(void)
      more careful! */
   qsort(ARR_GetElements(keys), ARR_GetSize(keys), sizeof (Key), compare_keys_by_id);
 
+  LOG(LOGS_INFO, "Loaded %u symmetric keys", ARR_GetSize(keys));
+
   /* Check for duplicates */
   for (i = 1; i < ARR_GetSize(keys); i++) {
     if (get_key(i - 1)->id == get_key(i)->id)