cmdmon: save NTS cookies and server keys on dump command

Extend the dump command to save also the server NTS keys and client NTS
cookies. Remove the warning for unset dumpdir.

ntp_auth.c

@@ -484,3 +484,17 @@ NAU_ChangeAddress(NAU_Instance instance, IPAddr *address)
       assert(0);
   }
 }
+
+/* ================================================== */
+
+void
+NAU_DumpData(NAU_Instance instance)
+{
+  switch (instance->mode) {
+    case NTP_AUTH_NTS:
+      NNC_DumpData(instance->nts);
+      break;
+    default:
+      break;
+  }
+}