[Backport 2.x] Avoid negative memory result in IndicesQueryCache stats calculation

[dbwiddis]

Backport c0a8cf8 from #6917.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/13349/
• CommitID: 3b94163
  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 (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.indices.replication.SegmentReplicationRelocationIT.testPrimaryRelocation
      1 org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=pit/10_basic/Delete all}

• URL: https://build.ci.opensearch.org/job/gradle-check/13627/
• CommitID: 3b94163
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov-commenter]

Codecov Report

Merging #6965 (5bf84ae) into 2.x (535cbac) will increase coverage by 0.19%.
The diff coverage is 100.00%.

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@@             Coverage Diff              @@
##                2.x    #6965      +/-   ##
============================================
+ Coverage     70.28%   70.47%   +0.19%     
- Complexity    59527    59592      +65     
============================================
  Files          4824     4824              
  Lines        286330   286332       +2     
  Branches      41626    41627       +1     
============================================
+ Hits         201250   201799     +549     
+ Misses        68279    67617     -662     
- Partials      16801    16916     +115     

Impacted Files	Coverage Δ
...java/org/opensearch/indices/IndicesQueryCache.java	88.48% <100.00%> (-2.76%)	⬇️

... and 480 files with indirect coverage changes

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[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.indices.replication.SegmentReplicationRelocationIT.testPrimaryRelocation

• URL: https://build.ci.opensearch.org/job/gradle-check/13828/
• CommitID: 5bf84ae
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.