RemoteClusterConnectionTests.testCloseWhileConcurrentlyConnecting sporadically fails

[javanna]

From https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+multijob-unix-compatibility/os=oraclelinux/811:

> Throwable #1: com.carrotsearch.randomizedtesting.UncaughtExceptionError: Captured an uncaught exception in thread: Thread[id=2346, name=elasticsearch[org.elasticsearch.action.search.RemoteClusterConnectionTests][management][T#2], state=RUNNABLE, group=TGRP-RemoteClusterConnectionTests]
   > 	at __randomizedtesting.SeedInfo.seed([635D3E120146B328:651D6287125AC38E]:0)
   > Caused by: java.lang.AssertionError: shit's been called twice
   > 	at __randomizedtesting.SeedInfo.seed([635D3E120146B328]:0)
   > 	at org.elasticsearch.action.search.RemoteClusterConnectionTests$4.lambda$run$1(RemoteClusterConnectionTests.java:497)
   > 	at org.elasticsearch.action.ActionListener$1.onFailure(ActionListener.java:68)
   > 	at org.elasticsearch.action.ActionListener.onFailure(ActionListener.java:102)
   > 	at org.elasticsearch.action.search.RemoteClusterConnection$ConnectHandler$1.lambda$doRun$1(RemoteClusterConnection.java:339)
   > 	at org.elasticsearch.action.ActionListener$1.onFailure(ActionListener.java:68)
   > 	at org.elasticsearch.action.search.RemoteClusterConnection$ConnectHandler$SniffClusterStateResponseHandler.handleResponse(RemoteClusterConnection.java:485)
   > 	at org.elasticsearch.action.search.RemoteClusterConnection$ConnectHandler$SniffClusterStateResponseHandler.handleResponse(RemoteClusterConnection.java:432)
   > 	at org.elasticsearch.transport.TransportService$ContextRestoreResponseHandler.handleResponse(TransportService.java:1030)
   > 	at org.elasticsearch.transport.TransportService$ContextRestoreResponseHandler.handleResponse(TransportService.java:1030)
   > 	at org.elasticsearch.transport.TcpTransport$2.doRun(TcpTransport.java:1379)
   > 	at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:638)
   > 	at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37)
   > 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
   > 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
   > 	at java.lang.Thread.run(Thread.java:745)
   > Caused by: java.lang.RuntimeException
   > 	at org.elasticsearch.action.search.RemoteClusterConnectionTests$4.lambda$run$1(RemoteClusterConnectionTests.java:494)
   > 	at org.elasticsearch.action.ActionListener$1.onFailure(ActionListener.java:68)
   > 	at org.elasticsearch.action.ActionListener.onFailure(ActionListener.java:102)
   > 	at org.elasticsearch.action.search.RemoteClusterConnection$ConnectHandler$1.lambda$doRun$1(RemoteClusterConnection.java:339)
   > 	at org.elasticsearch.action.ActionListener$1.onFailure(ActionListener.java:68)
   > 	at org.elasticsearch.action.search.RemoteClusterConnection$ConnectHandler.collectRemoteNodes(RemoteClusterConnection.java:400)
   > 	at org.elasticsearch.action.search.RemoteClusterConnection$ConnectHandler$1.doRun(RemoteClusterConnection.java:344)
   > 	at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37)
   > 	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
   > 	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
   > 	at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingRunnable.run(ThreadContext.java:569)
   > 	... 3 more

I couldn't reproduce this failure.