fix: test broke after #951

[jansegre]

Motivation

CI broke after #951 but the fix is trivial.

Acceptance Criteria

• Use unsafe_set (renamed method) instead of set (old method)
• All tests should pass

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (1f68ec7) 85.42% compared to head (d885d7f) 85.28%.
Report is 1 commits behind head on master.

Files	Patch %	Lines
hathor/sysctl/runner.py	75.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #953      +/-   ##
==========================================
- Coverage   85.42%   85.28%   -0.14%     
==========================================
  Files         292      292              
  Lines       22568    22581      +13     
  Branches     3395     3401       +6     
==========================================
- Hits        19278    19258      -20     
- Misses       2621     2645      +24     
- Partials      669      678       +9     

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