fix send start msg (#50085)

paddle/fluid/distributed/fleet_executor/carrier.cc

@@ -179,6 +179,7 @@ void Carrier::Start() {
                         "Using carrier before initialized."));
   InterceptorMessage start_msg;
   start_msg.set_dst_id(SOURCE_ID);
+  start_msg.set_src_id(SOURCE_ID);
   start_msg.set_message_type(START);
   Send(start_msg);
   // TODO(wangxi): async step