improve(modbus): speed up the recovery the modbus rtu

plugins/modbus/modbus_req.c

@@ -159,6 +159,7 @@ int modbus_group_timer(neu_plugin_t *plugin, neu_plugin_group_t *group,
             modbus_value_handle(plugin, gd->cmd_sort->cmd[i].slave_id, 0, NULL,
                                 NEU_ERR_PLUGIN_DISCONNECTED);
             rtt = NEU_METRIC_LAST_RTT_MS_MAX;
+            neu_conn_disconnect(plugin->conn);
         }
         if (plugin->interval > 0) {
             struct timespec t1 = { .tv_sec  = plugin->interval / 1000,

src/event/event_linux.c

@@ -89,10 +89,6 @@ static void *event_loop(void *arg)
             continue;
         }
 
-        if (ret == -1) {
-            continue;
-        }
-
         if (ret == -1 || events->stop) {
             zlog_warn(neuron, "event loop exit, errno: %s(%d), stop: %d",
                       strerror(errno), errno, events->stop);