Fix flaky ScalingThreadPoolTests.testScalingThreadPoolConfiguration test

[ashking94]

Description

The threadpool size in the main source code and the expected size in test code were different causing flaky test. This PR fixes the expected size in the test code.

Related Issues

Resolves #7530

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/15299/
• CommitID: 1600abf
  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?

[ashking94]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/15299/
• CommitID: 1600abf
  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?

Flay tests - https://build.ci.opensearch.org/job/gradle-check/15299/#showFailuresLink

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/15301/
• CommitID: 4d26694
  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?

[ashking94]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/15301/
• CommitID: 4d26694
  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?

Unrelated continuous build failures for all PR builds happening and on main branch - #7540

[reta]

@ashking94 could you rebase please?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/15325/
• CommitID: c1d1a5a

[codecov]

Codecov Report

Merging #7539 (c1d1a5a) into main (d9f840f) will decrease coverage by 0.06%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##               main    #7539      +/-   ##
============================================
- Coverage     70.58%   70.52%   -0.06%     
+ Complexity    59757    59727      -30     
============================================
  Files          4896     4896              
  Lines        286779   286779              
  Branches      41331    41331              
============================================
- Hits         202418   202251     -167     
- Misses        67647    67851     +204     
+ Partials      16714    16677      -37     

see 465 files with indirect coverage changes

[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:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/backport-2.x
# Create a new branch
git switch --create backport/backport-7539-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 b1871df36e3a80479ee4b461478ee45d8d308d10
# Push it to GitHub
git push --set-upstream origin backport/backport-7539-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-7539-to-2.x.

[reta]

@ashking94 sadly manual backport is needed to 2.x, could you please take it? thank you