Flaky-test: PulsarWorkerRebalanceDrainTest.testRebalanceWorkers. Function worker leader changes unpredictably causing flakiness.

### Search before reporting

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

### Example failure

https://gist.github.com/ShivrajJ/134d23d79a6e122677fd5b300c4de3fa

### Exception stacktrace

I added a debug-level log with the topic stats, so line numbers in the stack trace might be offset a little, see https://github.com/cognitree/pulsar/pull/22 for the changes

```text
Expected :true
Actual :false

java.lang.AssertionError:
at org.testng.Assert.fail(Assert.java:110)
at org.testng.Assert.failNotEquals(Assert.java:1577)
at org.testng.Assert.assertTrue(Assert.java:56)
at org.testng.Assert.assertTrue(Assert.java:66)
at org.apache.pulsar.tests.integration.functions.java.PulsarWorkerRebalanceDrainTest.testRebalance(PulsarWorkerRebalanceDrainTest.java:350)
at org.apache.pulsar.tests.integration.functions.java.PulsarWorkerRebalanceDrainTest.testRebalanceWorkers(PulsarWorkerRebalanceDrainTest.java:70)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at org.testng.internal.invokers.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:139)
at org.testng.internal.invokers.TestInvoker.invokeMethod(TestInvoker.java:677)
at org.testng.internal.invokers.TestInvoker.invokeTestMethod(TestInvoker.java:221)
at org.testng.internal.invokers.MethodRunner.runInSequence(MethodRunner.java:50)
at org.testng.internal.invokers.TestInvoker$MethodInvocationAgent.invoke(TestInvoker.java:969)
at org.testng.internal.invokers.TestInvoker.invokeTestMethods(TestInvoker.java:194)
at org.testng.internal.invokers.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:148)
at org.testng.internal.invokers.TestMethodWorker.run(TestMethodWorker.java:128)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
at org.testng.TestRunner.privateRun(TestRunner.java:829)
at org.testng.TestRunner.run(TestRunner.java:602)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:437)
at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:431)
at org.testng.SuiteRunner.privateRun(SuiteRunner.java:391)
at org.testng.SuiteRunner.run(SuiteRunner.java:330)
at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:95)
at org.testng.TestNG.runSuitesSequentially(TestNG.java:1256)
at org.testng.TestNG.runSuitesLocally(TestNG.java:1176)
at org.testng.TestNG.runSuites(TestNG.java:1099)
at org.testng.TestNG.run(TestNG.java:1067)
at com.intellij.rt.testng.IDEARemoteTestNG.run(IDEARemoteTestNG.java:65)
at com.intellij.rt.testng.RemoteTestNGStarter.main(RemoteTestNGStarter.java:105)
```

### Are you willing to submit a PR?

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

Start by locating PulsarWorkerRebalanceDrainTest.java and reading testRebalanceWorkers and testRebalance around lines 70 and 350. Run the integration test and compare its behavior with the linked failure details and topic-stat logs. Done means the rebalance test no longer fails because the worker leader changes unpredictably.

Written by the indexing model from the issue text.