Apt - fix for non-sec updates getting misclassified & related tmp cleanup

[kjohn-msft]

Discrepancies between pro client checks and sources checks suggested there was mistake in recent code on non-security package classification on Apt.

• All security updates remained correctly classified.
• Non-security updates on apt were getting misidentified in sources checks but correctly caught in pro client checks.

The false-positive wasn't immediately apparent in past extensive testing and was self-identified.

This PR also addresses a related problem to the code that went in - additional folder cleanup is required to cleanup artifacts from dynamic source calculation. This is covered now.

Log:
42.core.log

[codecov]

Codecov Report

Attention: Patch coverage is 98.50746% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.43%. Comparing base (bd5a687) to head (e1f4b9a).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/core/tests/Test_CoreMain.py	94.44%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #295      +/-   ##
==========================================
+ Coverage   92.42%   92.43%   +0.01%     
==========================================
  Files          97       97              
  Lines       16199    16226      +27     
==========================================
+ Hits        14972    14999      +27     
  Misses       1227     1227              

Flag	Coverage Δ
python27	92.43% <98.50%> (+0.01%)	⬆️
python39	92.43% <98.50%> (+0.01%)	⬆️

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