[ci] MockTcpTransportTests.testNotifyOnShutdown

[andyb-elastic]

Doesn't reproduce locally on master

https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+multijob-unix-compatibility/os=oraclelinux/2617/console

build-2617.txt

ERROR   0.10s J0 | MockTcpTransportTests.testNotifyOnShutdown <<< FAILURES!
   > Throwable #1: com.carrotsearch.randomizedtesting.UncaughtExceptionError: Captured an uncaught exception in thread: Thread[id=432, name=elasticsearch[org.elasticsearch.transport.MockTcpTransportTests][generic][T#1], state=RUNNABLE, group=TGRP-MockTcpTransportTests]
   >    at __randomizedtesting.SeedInfo.seed([CBC399AED8F96471:26E336404194B6E]:0)
   > Caused by: java.lang.AssertionError: Can't move to stopped state when closed
   >    at __randomizedtesting.SeedInfo.seed([CBC399AED8F96471]:0)
   >    at org.elasticsearch.transport.AbstractSimpleTransportTestCase.lambda$testNotifyOnShutdown$10(AbstractSimpleTransportTestCase.java:775)
   >    at org.elasticsearch.transport.RequestHandlerRegistry.processMessageReceived(RequestHandlerRegistry.java:63)
   >    at org.elasticsearch.transport.TcpTransport$RequestHandler.doRun(TcpTransport.java:1497)
   >    at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:723)
   >    at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37)
   >    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
   >    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
   >    at java.lang.Thread.run(Thread.java:748)

./gradlew :test:framework:test -Dtests.seed=CBC399AED8F96471 -Dtests.class=org.elasticsearch.transport.MockTcpTransportTests -Dtests.method="testNotifyOnShutdown" -Dtests.security.manager=true -Dtests.locale=el-CY -Dtests.timezone=IST -Dcompiler.java=10 -Druntime.java=8

[original-brownbear]

Looking into it, I can reproduce it by running the test in a loop (like 1/5k runs only though)