Flaky test case for testGraphQueryErrorsGetIncremented

[jmazanec15]

Response exception is not being thrown when it should - https://github.com/opensearch-project/k-NN/pull/34/checks?check_run_id=2822356887. Only happens occassionally.

 org.opensearch.knn.plugin.action.RestKNNStatsHandlerIT > testGraphQueryErrorsGetIncremented FAILED
    junit.framework.AssertionFailedError: Expected exception ResponseException but no exception was thrown
        at __randomizedtesting.SeedInfo.seed([4D0A87CF2F3FABDE:3B0431BAFE8AE542]:0)
        at org.apache.lucene.util.LuceneTestCase.expectThrows(LuceneTestCase.java:2744)
        at org.apache.lucene.util.LuceneTestCase.expectThrows(LuceneTestCase.java:2734)
        at org.opensearch.knn.plugin.action.RestKNNStatsHandlerIT.testGraphQueryErrorsGetIncremented(RestKNNStatsHandlerIT.java:192)

Related to this line. It expects CB to be tripped so that query will fail, but its not getting tripped.