[BUG] ClusterMaxMergesAtOnceIT is flaky #18056
Description
Describe the bug
This is a new test that fails with the seed below. I'm creating this issue to force a follow up as I will be muting this IT.
Related component
Indexing
To Reproduce
./gradlew ':server:internalClusterTest' --tests "org.opensearch.index.ClusterMaxMergesAtOnceIT.testClusterLevelDefaultUpdatesMergePolicy" -Dtests.seed=2BD0981DD7D9F5EF
ClusterMaxMergesAtOnceIT > testClusterLevelDefaultUpdatesMergePolicy FAILED
java.lang.NullPointerException: Cannot invoke "org.opensearch.index.IndexService.getIndexSettings()" because "thirdIndexService" is null
at __randomizedtesting.SeedInfo.seed([2BD0981DD7D9F5EF:5E508FCB086B2864]:0)
at org.opensearch.index.ClusterMaxMergesAtOnceIT.testClusterLevelDefaultUpdatesMergePolicy(ClusterMaxMergesAtOnceIT.java:110)
Expected behavior
Test should not be flaky
Additional Details
No response