Flaky-test: BookieZKExpireTest.testBookieServerZKExpireBehaviour

[hangc0276]

When running CI, the test occasionally with the following exception

Error:  org.apache.bookkeeper.test.BookieZKExpireTest.testBookieServerZKExpireBehaviour  Time elapsed: 16.286 s  <<< FAILURE!
java.lang.AssertionError: Bookie should not shutdown on losing zk session
	at org.junit.Assert.fail(Assert.java:88)
	at org.junit.Assert.assertTrue(Assert.java:41)
	at org.apache.bookkeeper.test.BookieZKExpireTest.testBookieServerZKExpireBehaviour(BookieZKExpireTest.java:103)
	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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.junit.internal.runners.statements.FailOnTimeout$CallableStatement.call(FailOnTimeout.java:298)
	at org.junit.internal.runners.statements.FailOnTimeout$CallableStatement.call(FailOnTimeout.java:292)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.lang.Thread.run(Thread.java:829)

[dlg99]

The problem does not repro locally (macbook, ran test in a loop 100 times - all successes)

Reproed by running in a docker limited to 2 cpus, log:
org.apache.bookkeeper.test.BookieZKExpireTest-output.txt

[dlg99]

Fixed