add more test for fixedFeedbackRate controller implementation

[tunedev]

Checklist

• A link to the issue/user story that the pull request relates to
• How to recreate the problem without the fix
• Design of the fix
• How to prove that the fix works
• Automated tests that prove the fix keeps on working
• Documentation - any JSDoc, website, or Stackoverflow answers?

Issue/User story

Partially addresses #1606

Steps to Reproduce

Existing issues

• Stack Overflow issues
• GitHub Issues
• Discord history

Design of the fix

Validation of the fix

After this PR: Running the tests in caliper-core the listed %stmts in the code coverage report should tally with the below listed

• caliper-core/lib/worker/fixedFeedbackRate.js: 80

Before the PR: Running the tests in caliper-core the listed %stmts in the code coverage report the below listed was what was there before

• caliper-core/lib/worker/fixedFeedbackRate.js: 60

What documentation has been provided for this pull request

[davidkel]

Sorry, this is going to be a hard one to test and make sure that the descriptions of the tests provide detail. Unfortunately the original tests are not ideal either but I don't think we should follow the same pattern as this file if we know they are not ideal. If possible it would be nice to update them but I think that would have to be an exercise for later.

However I saw you correctly used async/await in your tests and the original ones didn't, so a quick update worth doing would be to apply that pattern to the original tests.