Remove unnecessary code from is_cgroups_supported

[pgombar]

Description

Remove leftover and incorrect code that references WSL and Trusty. The only criteria for determining if cgroups is supported is if the path /sys/fs/cgroups exists or not.

Issue #1597

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PR information

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• There are a small number of commits, each of which has an informative message. This means that previously merged commits do not appear in the history of the PR. For information on cleaning up the commits in your pull request, see this page.
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Quality of Code and Contribution Guidelines

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This change is 

[codecov]

Codecov Report

Merging #1599 into develop will increase coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop    #1599      +/-   ##
===========================================
+ Coverage    66.01%   66.02%   +<.01%     
===========================================
  Files           77       77              
  Lines        11053    11048       -5     
  Branches      1559     1558       -1     
===========================================
- Hits          7297     7294       -3     
+ Misses        3421     3420       -1     
+ Partials       335      334       -1

Impacted Files	Coverage Δ
azurelinuxagent/common/osutil/default.py	57.73% <100%> (-0.02%)	⬇️

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[plessisa]

Do we know what is the release targeted to this fix? Seems like it did not made it to 2.2.42.

[narrieta]

@plessisa - we are targeting a release by end of next week

[narrieta]

Fixes #1597