IOS上显示不了cocos-lua控件树

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**(重要！问题分类)**
* 控件识别、树状结构、poco库报错

**描述问题bug**
连接IOS设备后，能显示投屏，能显示IOS控件树，显示不了cocos-lua控件树。但是用PocoHierarchyViewer可以正常显示cocos-lua控件树，poco用的端口是15004

AirtestIDE有报错
```
initializing Cocos poco.
[rpc]connected
[Errno 54] Connection reset by peer
retry to connect, error: ('Connection aborted.', ConnectionRefusedError(61, 'Connection refused'))
[Errno 32] Broken pipe
retry to connect, error: ('Connection aborted.', ConnectionRefusedError(61, 'Connection refused'))
closing Cocos Poco.
Traceback (most recent call last):
File "/Users/wjjn3033/dev/idestable/airtest-ide/app/plugins/poco/poco_probe.py", line 170, in close
File "/Applications/AirtestIDE.app/Contents/MacOS/poco/utils/simplerpc/rpcclient.py", line 44, in close
self.conn.close()
File "/Applications/AirtestIDE.app/Contents/MacOS/poco/utils/simplerpc/transport/tcp/main.py", line 43, in close
self.c.close()
File "/Applications/AirtestIDE.app/Contents/MacOS/poco/utils/simplerpc/transport/tcp/safetcp.py", line 72, in close
self.sock.shutdown(socket.SHUT_RDWR)
OSError: [Errno 57] Socket is not connected

retry to connect, error: ('Connection aborted.', ConnectionRefusedError(61, 'Connection refused'))
Traceback (most recent call last):
File "/Users/wjjn3033/dev/idestable/airtest-ide/app/plugins/poco/poco_probe.py", line 138, in initPoco
File "/Applications/AirtestIDE.app/Contents/MacOS/airtest/core/ios/instruct_helper.py", line 67, in do_proxy
raise AirtestError((stdout, stderr))
airtest.core.error.AirtestError: ('', 'bind(): Address already in use\nError creating socket: Address already in use\n')

```

**复现步骤**
1. 按照 http://airtest.netease.com/docs/cn/2_device_connection/4_ios_connection.html 操作
2. 启动 iOS-Tagent的test， 启动游戏
3. 连接设备

**预期效果**
预期可以看到cocos-lua的控件树

**相关截图**
(贴出遇到问题时的截图内容，如果有的话)

**python 版本:** `Python 2.7.10 `

**poco 版本:** `1.0.7`

**设备:**
- 型号: iPad6,11
- 系统: 11.4.1

**其他相关环境信息**
macOS 10.13.6
AirtestIDE 1.2.0