Island: Add a small throttle to shorten the OTP

[VakarisZ]

What does this PR do?

Part of #4187

Calculations

7 chars (alphanumeric + 3 special characters) gives total of 4,764,996,883,946 combinations (based on this
The current throttle is 0.001, so the result is that you're able to check 120 000 passwords per 2 minutes.
This means that you chance of guessing the OTP is 1 in 39,708,307. In practice it's much higher if you account for network latency. I think this is sufficient security for a problem whose real solution is NAC.

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?
• Have you checked that you haven't introduced any duplicate code?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.06%. Comparing base (af54997) to head (cee2e2f).

❗ Current head cee2e2f differs from pull request most recent head 3ccd633

Please upload reports for the commit 3ccd633 to get more accurate results.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #4188   +/-   ##
========================================
  Coverage    77.06%   77.06%           
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  Files          442      442           
  Lines        14125    14126    +1     
  Branches        18       18           
========================================
+ Hits         10885    10886    +1     
  Misses        3240     3240           

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[mssalvatore]

Any reason not to squash these two commits together?