Keep full router jitter precision in monitor snapshots

src/control_server.c

@@ -1281,7 +1281,7 @@ static void send_metrics(struct control_server* server, struct control_client* c
                 rtt_cnt++;
             }
             {
-                uint16_t j = (uint16_t)(rc->rtt_jitter / 32768);
+                uint32_t j = rc->rtt_jitter / 32768;
                 if (j > rsp->router.jitter) rsp->router.jitter = j;
             }
             if (rc->minrtt_window_count > 0) {