Linux ubuntu下多机执行任务偶现Failed to establish a new connection错误

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**(重要！问题分类)**
* 图像识别、设备控制相关问题 -> 按下面的步骤

**描述问题bug**
Linux ubuntu下多机执行任务，会偶现Failed to establish a new connection的问题，在windows下没有出现
```
et1.11.7: Traceback (most recent call last):
File "/home/mfs/mtp_resource/gitUiCase/testcase/platformgroup/usersystem/test_user.py", line 11, in setUp
base.changeEnv("2")
File "/home/mfs/mtp_resource/gitUiCase/testcase/platformgroup/platfbase.py", line 161, in changeEnv
if poco("*****android:id/skip_btn").exists():
File "/home/mtp/.local/lib/python2.7/site-packages/poco/proxy.py", line 72, in wrapped
return func(proxy, *args, **kwargs)
File "/home/mtp/.local/lib/python2.7/site-packages/poco/proxy.py", line 774, in exists
return self.attr('visible')
File "/home/mtp/.local/lib/python2.7/site-packages/poco/proxy.py", line 39, in wrapped
return func(self, *args, **kwargs)
File "/home/mtp/.local/lib/python2.7/site-packages/poco/proxy.py", line 734, in attr
nodes = self._do_query(multiple=False)
File "/home/mtp/.local/lib/python2.7/site-packages/poco/proxy.py", line 872, in _do_query
self._nodes = self.poco.agent.hierarchy.select(self.query, multiple)
File "/home/mtp/.local/lib/python2.7/site-packages/poco/utils/retry.py", line 20, in wrapped
raise ex
TransportDisconnected: HTTPConnectionPool(host='127.0.0.1', port=11200): Max retries exceeded with url: / (Caused by NewConnectionError(': Failed to establish a new connection: [Errno 111] Connection refused',))
```

**python 版本:** `python2.7`

**airtest 版本:** `1.0.27`
> airtest版本通过`pip freeze`可以命令可以查到

**设备:**
- 型号: [华为Mate20 X，华为nova 2s]
- 系统: [Android 9]
- (别的信息)

**其他相关环境信息**
多机运行在linux ubuntu16.04上运行异常，在windows上正常。