Fix Flaky Test SpecificClusterManagerNodesIT.testElectOnlyBetweenClusterManagerNodes

[kkewwei]

Description

When we call the code, the cluster manager is being removed from cluster, it will happen in internalCluster().nonClusterManagerClient() or getClusterManagerNode():
https://github.com/opensearch-project/OpenSearch/blob/main/server/src/internalClusterTest/java/org/opensearch/cluster/SpecificClusterManagerNodesIT.java#L63C9-L79C10

• When it happens in internalCluster().nonClusterManagerClient(), which hit the case in Fix Flaky Test SpecificClusterManagerNodesIT.testElectOnlyBetweenClusterManagerNodes #16021.
• When it happens in getClusterManagerNode(), which hit the current case, and we will fix it in the pr. Details can be seen in [BUG] org.opensearch.cluster.SpecificClusterManagerNodesIT.testElectOnlyBetweenClusterManagerNodes is flaky #16015 (comment)

Related Issues

Resolves #15944 #16015

Check List

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

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[github-actions]

❌ Gradle check result for eb0a6a8: 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 91b5b6d: 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?

[kkewwei]

@gaobinlon, could you review it in your spare time.

[github-actions]

❕ Gradle check result for 91b5b6d: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.snapshots.DedicatedClusterSnapshotRestoreIT.testSnapshotWithStuckNode

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]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.45%. Comparing base (af5835f) to head (91b5b6d).
Report is 263 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main   #17640   +/-   ##
=========================================
  Coverage     72.44%   72.45%           
+ Complexity    65732    65707   -25     
=========================================
  Files          5311     5311           
  Lines        305011   305011           
  Branches      44232    44232           
=========================================
+ Hits         220969   220983   +14     
+ Misses        65967    65905   -62     
- Partials      18075    18123   +48     

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