Fix flaky terminaton conditions for org.opensearch.rest.ReactorNetty4StreamingStressIT.testCloseClientStreamingRequest test case

[reta]

Description

Followup on this comment #15859 (comment), removal of the ConnectionClosedException was premature:

java.lang.AssertionError: expectation "expectErrorMatches" failed (predicate failed on exception: org.apache.hc.core5.http.ConnectionClosedException: Connection is closed)
	at __randomizedtesting.SeedInfo.seed([7B0D53ACECB8DFD0:E2197F8350CD27C2]:0)
	at reactor.test.MessageFormatter.assertionError(MessageFormatter.java:115)
	at reactor.test.MessageFormatter.failPrefix(MessageFormatter.java:104)
	at reactor.test.MessageFormatter.fail(MessageFormatter.java:73)

• https://build.ci.opensearch.org/job/gradle-check/47887/testReport/org.opensearch.rest/ReactorNetty4StreamingStressIT/testCloseClientStreamingRequest/
• https://build.ci.opensearch.org/job/gradle-check/47887/testReport/junit/org.opensearch.rest/ReactorNetty4StreamingStressIT/testCloseClientStreamingRequest/

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[reta]

@mch2 may I ask you please to take a look? thank you!

[github-actions]

❌ Gradle check result for 85ebbb0: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

✅ Gradle check result for 85ebbb0: SUCCESS

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.84%. Comparing base (c709400) to head (85ebbb0).
Report is 5 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #15959      +/-   ##
============================================
- Coverage     71.93%   71.84%   -0.10%     
+ Complexity    64374    64306      -68     
============================================
  Files          5277     5277              
  Lines        300828   300828              
  Branches      43474    43474              
============================================
- Hits         216411   216126     -285     
- Misses        66725    66953     +228     
- Partials      17692    17749      +57     

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[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/OpenSearch/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-2.x
# Create a new branch
git switch --create backport/backport-15959-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 eb5b70370e548cd0f3b51721397df818b3050daa
# Push it to GitHub
git push --set-upstream origin backport/backport-15959-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-15959-to-2.x.