Fix: regressions

[dorianim]

Description

This issues fixes three regressions:

1. The setup did not work anymore
2. Clearing the sssd user cache in prepare-image did not work
3. In some places a confusing ERROR was logged

See also https://ask.linuxmuster.net/t/debian-13-totaler-anfang/11985/4

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Unittests
• Debian 13

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[codecov]

Codecov Report

❌ Patch coverage is 30.00000% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.82%. Comparing base (5c846a2) to head (cf465b2).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
...st-packages/linuxmusterLinuxclient7/imageHelper.py	0.00%	5 Missing ⚠️
...on3/dist-packages/linuxmusterLinuxclient7/setup.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #91      +/-   ##
==========================================
- Coverage   61.93%   61.82%   -0.12%     
==========================================
  Files          18       18              
  Lines        1542     1548       +6     
==========================================
+ Hits          955      957       +2     
- Misses        587      591       +4     

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