[CI] testEnsureWeReconnect fails recently

[dnhatn]

RemoteClusterClientTests#testEnsureWeReconnect fails recently but it is not reproducible locally.

Log: reconnect.txt

   > 	at org.elasticsearch.transport.RemoteClusterClientTests.lambda$testEnsureWeReconnect$1(RemoteClusterClientTests.java:85)
   > 	at org.elasticsearch.test.ESTestCase.assertBusy(ESTestCase.java:751)
   > 	at org.elasticsearch.test.ESTestCase.assertBusy(ESTestCase.java:725)
   > 	at org.elasticsearch.transport.RemoteClusterClientTests.testEnsureWeReconnect(RemoteClusterClientTests.java:85)
   > 	at java.lang.Thread.run(Thread.java:748)
   > 	Suppressed: java.lang.AssertionError
   > 		at org.elasticsearch.transport.RemoteClusterClientTests.lambda$testEnsureWeReconnect$1(RemoteClusterClientTests.java:85)
   > 		at org.elasticsearch.test.ESTestCase.assertBusy(ESTestCase.java:739)
   > 		... 39 more

Some instances:

1. https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+multijob-unix-compatibility/os=centos/2320/console

2. https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+6.x+multijob-unix-compatibility/os=amazon/945/console

[elasticmachine]

Pinging @elastic/es-core-infra

[dnhatn]

I muted the test in fd161d2