[Backport 2.x] Fix flaky test MoreExpressionIT.testSpecialValueVariable in concurrent search path

[sohami]

Description

Backport f4b25d6 from #11088.

Related Issues

Resolves #10079

Check List

• New functionality includes testing.
  • All tests pass
    New functionality has been documented.
    New functionality has javadoc added
    Failing checks are inspected and point to the corresponding known issue(s) (See: Troubleshooting Failing Builds)
• Commits are signed per the DCO using --signoff
  Commit changes are listed out in CHANGELOG.md file (See: Changelog)
  Public documentation issue/PR created

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[github-actions]

Compatibility status:

Checks if related components are compatible with change c0cbb24

Incompatible components

Incompatible components: [https://github.com/opensearch-project/performance-analyzer.git]

Skipped components

Compatible components

Compatible components: [https://github.com/opensearch-project/security-analytics.git, https://github.com/opensearch-project/custom-codecs.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/neural-search.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/security.git, https://github.com/opensearch-project/asynchronous-search.git, https://github.com/opensearch-project/reporting.git, https://github.com/opensearch-project/index-management.git, https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/anomaly-detection.git, https://github.com/opensearch-project/k-nn.git, https://github.com/opensearch-project/performance-analyzer-rca.git, https://github.com/opensearch-project/alerting.git]

[github-actions]

✅ Gradle check result for c0cbb24: SUCCESS

[codecov]

Codecov Report

Attention: 16 lines in your changes are missing coverage. Please review.

Comparison is base (2494528) 71.04% compared to head (c0cbb24) 70.98%.

Files	Patch %	Lines
...on/PerThreadReplaceableConstDoubleValueSource.java	0.00%	11 Missing ⚠️
...arch/script/expression/ExpressionScriptEngine.java	0.00%	4 Missing ⚠️
...script/expression/ExpressionAggregationScript.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #11309      +/-   ##
============================================
- Coverage     71.04%   70.98%   -0.06%     
+ Complexity    59111    59046      -65     
============================================
  Files          4869     4869              
  Lines        278654   278660       +6     
  Branches      40830    40831       +1     
============================================
- Hits         197982   197820     -162     
- Misses        63895    64096     +201     
+ Partials      16777    16744      -33     

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