Investigate why test_cuberite_agent_connection is failing on #773

## Type of Issue

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- [x] Bug report (to report a bug)
- [ ] Feature request (to request an additional feature)
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- [ ] Refactor request
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## Description

The MC unittest `test_cuberite_agent_connection` is failing after #773 is merged. Investigate this issue and bring this unittest back once figure it out (#810 ). The problems here are:

1. the changes of #773 seems totally irrelevant to this unittest
2. the unittest usually fails but also can pass transiently
3. reran CI with ssh and sshed into CI env to the same command, I obvserved the unittest is actually passing.

## Steps to reproduce

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## Links to any relevant pastes or documents

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## Checklist

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