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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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

:exclamation: Current head cee2e2f differs from pull request most recent head 3ccd633

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Additional details and impacted files

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

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