Fixes data loss for the log rotator

[FedericoPonzi]

Motivation and Context

The last feature merged, the log rotation, had a flaky test randomly failing. See the last deps update merged to master: https://github.com/FedericoPonzi/Horust/actions/runs/11583491268/attempts/1

Description

This is from BufReader description:

When the BufReader is dropped, the contents of its buffer will be discarded. Creating multiple instances of a BufReader on the same stream can cause data loss.
Now one BufReader is created at the beginning and held throughout.

How Has This Been Tested?

Generally improved the associated test by removing some magic. Now it seems to be working very well, consistently passing the test.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (a change to man pages or other documentation)

Checklist:

• I have updated the documentation accordingly.
• I have added tests to cover my changes.