Flaky-test: BatchMessageWithBatchIndexLevelTest.testBatchMessageAck

### Search before asking

- [X] I searched in the [issues](https://github.com/apache/pulsar/issues) and found nothing similar.

### Example failure

https://github.com/apache/pulsar/runs/8104817693?check_suite_focus=true

### Exception stacktrace

```
Error: Tests run: 74, Failures: 1, Errors: 0, Skipped: 5, Time elapsed: 92.5 s <<< FAILURE! - in org.apache.pulsar.broker.service.BatchMessageWithBatchIndexLevelTest
Error: testBatchMessageAck(org.apache.pulsar.broker.service.BatchMessageWithBatchIndexLevelTest) Time elapsed: 10.399 s <<< FAILURE!
org.awaitility.core.ConditionTimeoutException: Assertion condition defined as a org.apache.pulsar.broker.service.BatchMessageWithBatchIndexLevelTest expected [0] but found [16] within 10 seconds.
at org.awaitility.core.ConditionAwaiter.await(ConditionAwaiter.java:167)
at org.awaitility.core.AssertionCondition.await(AssertionCondition.java:119)
at org.awaitility.core.AssertionCondition.await(AssertionCondition.java:31)
at org.awaitility.core.ConditionFactory.until(ConditionFactory.java:985)
at org.awaitility.core.ConditionFactory.untilAsserted(ConditionFactory.java:769)
at org.apache.pulsar.broker.service.BatchMessageWithBatchIndexLevelTest.testBatchMessageAck(BatchMessageWithBatchIndexLevelTest.java:106)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:132)
at org.testng.internal.InvokeMethodRunnable.runOne(InvokeMethodRunnable.java:45)
at org.testng.internal.InvokeMethodRunnable.call(InvokeMethodRunnable.java:73)
at org.testng.internal.InvokeMethodRunnable.call(InvokeMethodRunnable.java:11)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: java.lang.AssertionError: expected [0] but found [16]
at org.testng.Assert.fail(Assert.java:99)
at org.testng.Assert.failNotEquals(Assert.java:1037)
at org.testng.Assert.assertEqualsImpl(Assert.java:140)
at org.testng.Assert.assertEquals(Assert.java:122)
at org.testng.Assert.assertEquals(Assert.java:907)
at org.testng.Assert.assertEquals(Assert.java:917)
at org.apache.pulsar.broker.service.BatchMessageWithBatchIndexLevelTest.lambda$testBatchMessageAck$2(BatchMessageWithBatchIndexLevelTest.java:107)
at org.awaitility.core.AssertionCondition.lambda$new$0(AssertionCondition.java:53)
at org.awaitility.core.ConditionAwaiter$ConditionPoller.call(ConditionAwaiter.java:248)
at org.awaitility.core.ConditionAwaiter$ConditionPoller.call(ConditionAwaiter.java:235)
... 4 more
```

### Are you willing to submit a PR?

- [ ] I'm willing to submit a PR!

Start by reviewing the merged pull request #17436, then inspect BatchMessageWithBatchIndexLevelTest.testBatchMessageAck around lines 106-107 and reproduce the referenced GitHub Actions failure. Done means the test no longer times out and its acknowledgement assertion passes reliably.

Written by the indexing model from the issue text.