[apache/incubator-teaclave] Execute builtin_echo.py error (#463)

[master-davidlee]

I have launched all the service 
![image](https://user-images.githubusercontent.com/49427668/105189064-896c3680-5b6f-11eb-881d-f0a3bf8f2023.png)
but when I want to run  the example  echo.py
![image](https://user-images.githubusercontent.com/49427668/105189161-a3a61480-5b6f-11eb-9b85-293382fdfd65.png)


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