Reset retries when acking pending I frames

src/server.c

@@ -1259,6 +1259,8 @@ static int frame_ack(patty_ax25_server *server,
         patty_timer_stop(&sock->timer_t1);
 
         if (patty_ax25_sock_ack_pending(sock) > 0) {
+            sock->retries = sock->n_retry;
+
             patty_timer_start(&sock->timer_t1);
         }
     }