Fix UNKNOWN(Zombie) Process in unexpected processes check

[nagworld9]

Description

/proc/{pid}/stat would provide the process state. The state 'Z' means, it's a zombie process and we consider it as valid one if found in agent cgroup.

Issue #

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PR information

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• New Unit tests were added for the changes made

Quality of Code and Contribution Guidelines

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[codecov]

Codecov Report

Merging #2644 (0639c30) into develop (1f84bac) will increase coverage by 0.00%.
The diff coverage is 81.81%.

@@           Coverage Diff            @@
##           develop    #2644   +/-   ##
========================================
  Coverage    72.02%   72.03%           
========================================
  Files          103      103           
  Lines        15745    15755   +10     
  Branches      2501     2502    +1     
========================================
+ Hits         11341    11349    +8     
- Misses        3887     3889    +2     
  Partials       517      517           

Impacted Files	Coverage Δ
azurelinuxagent/common/cgroupconfigurator.py	73.58% <81.81%> (+0.10%)	⬆️

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