[BUG] org.opensearch.backwards.IndexingIT is flaky

[ankitkala]

java.lang.NullPointerException: Cannot invoke "java.util.List.iterator()" because "shardStats" is null
	at __randomizedtesting.SeedInfo.seed([50FFF0AEEC143354:AA02D9ADCA8C830]:0)
	at org.opensearch.backwards.IndexingIT.buildShards(IndexingIT.java:511)
	at org.opensearch.backwards.IndexingIT.lambda$assertSeqNoOnShards$11(IndexingIT.java:484)
	at org.opensearch.test.OpenSearchTestCase.assertBusy(OpenSearchTestCase.java:1072)
	at org.opensearch.test.OpenSearchTestCase.assertBusy(OpenSearchTestCase.java:1057)
	at org.opensearch.backwards.IndexingIT.assertSeqNoOnShards(IndexingIT.java:482)
	at org.opensearch.backwards.IndexingIT.testIndexingWithReplicaOnBwcNodes(IndexingIT.java:204)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
	at java.base/java.lang.reflect.Method.invoke(Method.java:578)

• org.opensearch.backwards.IndexingIT.testIndexingWithReplicaOnBwcNodes
• org.opensearch.backwards.IndexingIT.testIndexVersionPropagation
• org.opensearch.backwards.IndexingIT.testIndexingWithPrimaryOnBwcNodes
• org.opensearch.backwards.IndexingIT.testSeqNoCheckpoints

https://build.ci.opensearch.org/job/gradle-check/22903/

[ashking94]

This test failure has not been reported since last 2-3 months. I am running this on loop to see if there are failures.

[ashking94]

Ran overnight for 1500 iterations and still running the IndexingIT class and no failures have occurred.

[ashking94]

This had ran for 7K iterations without any failure.