Flaky-test: ZKSessionTest.testSessionLost

Flaky-test: org.apache.pulsar.metadata.ZKSessionTest.testSessionLost
Number of failures: 5

org.apache.pulsar.metadata.ZKSessionTest is flaky. The testSessionLost test method fails sporadically.

```
java.lang.AssertionError: expected [Reconnected] but found [null]
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:617)
at org.apache.pulsar.metadata.ZKSessionTest.testSessionLost(ZKSessionTest.java:91)
```

Usage tip: To enable automatic navigation to failure message, open the following links with CTRL/CMD-click.
[example failure 2022-01-30T12:31:48.6236090Z](https://github.com/apache/pulsar/runs/4996482948?check_suite_focus=true?check_suite_focus=true#step:8:17798)
[example failure 2022-01-29T07:00:33.9978848Z](https://github.com/apache/pulsar/runs/4989658343?check_suite_focus=true?check_suite_focus=true#step:8:17794)
[example failure 2022-01-28T13:32:39.6065870Z](https://github.com/apache/pulsar/runs/4980584591?check_suite_focus=true?check_suite_focus=true#step:8:17794)
[example failure 2022-01-28T11:57:47.0870676Z](https://github.com/apache/pulsar/runs/4979694510?check_suite_focus=true?check_suite_focus=true#step:8:17794)
[example failure 2022-01-27T12:07:16.7537224Z](https://github.com/apache/pulsar/runs/4964582766?check_suite_focus=true?check_suite_focus=true#step:8:17794)

Full exception stacktrace

java.lang.AssertionError: expected [Reconnected] but found [null]

	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:617)

	at org.apache.pulsar.metadata.ZKSessionTest.testSessionLost(ZKSessionTest.java:91)

	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

	at java.base/java.lang.reflect.Method.invoke(Method.java:566)

	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:1128)

	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)

	at java.base/java.lang.Thread.run(Thread.java:829)

Start with org.apache.pulsar.metadata.ZKSessionTest.testSessionLost and the assertion at line 91, then review the linked CI failure runs to compare the sporadic failures. Reproduce the test and investigate why the expected Reconnected value is null; done means the test passes reliably without masking the session behavior.

Written by the indexing model from the issue text.