fix: 后端连接建立失败后，数据连接应该关闭

Author: meethigher

src/main/java/top/meethigher/proxy/tcp/tunnel/ReverseTcpProxyTunnelClient.java

@@ -232,6 +232,8 @@ protected boolean doHandle(Vertx vertx, NetSocket netSocket, TunnelMessageType t
                                             backendSocket.remoteAddress(),
                                             sessionId);
                                 } else {
+                                    // 建立连接失败，那么数据连接就要关闭
+                                    dataSocket.close();
                                     log.error("{}: client open backend connection to {}:{} failed",
                                             dataProxyName,
                                             backendHost, backendPort, rst.cause());