Fix breaking monkey on german system language by adding cp850 encoding to ping scanner

[TRGamer-tech]

What does this PR do?

Fixes #1175.

Add encoding cp850 to subprocess of ping scanner.
This adds the ability for the monkey to work on other system languages that use DOS-Latin-1 as encoding.

PR Checklist

• Have you added an explanation of what your changes do and why you'd like to include them?
• Is the TravisCI build passing?
• Was the CHANGELOG.md updated to reflect the changes?
• Was the documentation framework updated to reflect the changes?

Testing Checklist

• Added relevant unit tests?
• Have you successfully tested your changes locally? Elaborate:

  Tested by running the Monkey locally on a system using the german (and english of course) system language

• If applicable, add screenshots or log transcripts of the feature working

Explain Changes

Are the commit messages enough? If not, elaborate.

[codecov]

Codecov Report

Merging #1403 (54e519e) into develop (8e9f564) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           develop    #1403      +/-   ##
===========================================
- Coverage    40.07%   40.06%   -0.02%     
===========================================
  Files          465      465              
  Lines        13845    13849       +4     
===========================================
  Hits          5548     5548              
- Misses        8297     8301       +4     

Impacted Files	Coverage Δ
monkey/infection_monkey/network/ping_scanner.py	0.00% <0.00%> (ø)

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