Create new user with a random password

[shreyamalviya]

Fixes #1169

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:

  Ran the Island, configuration page loads properly. Swimm units work.

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

[codecov]

Codecov Report

Merging #1174 (c779655) into develop (ce6b658) will decrease coverage by 0.02%.
The diff coverage is 0.00%.

❗ Current head c779655 differs from pull request most recent head 58b04ec. Consider uploading reports for the commit 58b04ec to get more accurate results

@@             Coverage Diff             @@
##           develop    #1174      +/-   ##
===========================================
- Coverage    28.77%   28.75%   -0.03%     
===========================================
  Files          414      415       +1     
  Lines        12752    12760       +8     
===========================================
- Hits          3670     3669       -1     
- Misses        9082     9091       +9     

Impacted Files	Coverage Δ
monkey/infection_monkey/config.py	65.00% <ø> (-0.25%)	⬇️
monkey/infection_monkey/exploit/win_ms08_067.py	0.00% <0.00%> (ø)
...y/infection_monkey/post_breach/actions/add_user.py	0.00% <0.00%> (ø)
...nfection_monkey/utils/random_password_generator.py	0.00% <0.00%> (ø)
...onkey_island/cc/services/config_schema/internal.py	100.00% <ø> (ø)

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[VakarisZ]

Would be more readable if called random_password, because that's what it is in this context. It's not a password of remote user yet and pwd is not consistent (also means print working directory), either ..._pass or ..._password

[VakarisZ]

Create a constant here, called SECRET_BYTE_LENGTH and set it to 32. Then use this constant as a default parameter in get_random_password. 12 bytes is not enough.

[VakarisZ]

Small changes