[Filebeat][CometD] Resolve flaky unit test

[niraj-elastic]

• Cleanup

What does this PR do?

TestMultiEventForEOFRetryHandlerInput unit test of Filebeat CometD input is failing sometimes due to blockage of go channel . This unit test checks that CometD input is not closing input worker in case of client-server connection issue with EOF error.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @niraj-elastic? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v8./d.0 is the label to automatically backport to the 8./d branch. /d is the digit

[elasticmachine]

💚 Build Succeeded

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Build stats

• Start Time: 2023-04-03T11:20:13.461+0000

• Duration: 72 min 7 sec

Test stats 🧪

Test	Results
Failed	0
Passed	2875
Skipped	173
Total	3048

💚 Flaky test report

Tests succeeded.

🤖 GitHub comments

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[kush-elastic]

/test

[agithomas]

@ishleenk17 , kindly help by reviewing.

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b cometd_unit_test_update upstream/cometd_unit_test_update
git merge upstream/main
git push upstream cometd_unit_test_update

[ishleenk17]

Since this is a unit test having 2 events should be fine.
But, I hope this would work with more number of events as well.

[niraj-elastic]

Yes, Input works properly with more number of events. We have kept it to 2 for unit testing purpose only.

[ishleenk17]

Looks good!