[CI] SpecificMasterNodesIT#testElectOnlyBetweenMasterNodes fails

[cbuescher]

Seen at least three times in master in the last few days:

https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+internalClusterTest/497/console
https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+intake/1777/console
https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+intake/1710/console

Latest reproduce line:

./gradlew :server:integTest \
  -Dtests.seed=2CFBF83AF54213EC \
  -Dtests.class=org.elasticsearch.cluster.SpecificMasterNodesIT \
  -Dtests.method="testElectOnlyBetweenMasterNodes" \
  -Dtests.security.manager=true \
  -Dtests.locale=ar-DZ \
  -Dtests.timezone=Africa/Kinshasa \
  -Dcompiler.java=11 \
  -Druntime.java=8

Running repeatedly on Ubuntu didn't reproduce after 50 runs.

Logs contain NPEs:

14:52:15   1> java.lang.NullPointerException: null
14:52:15   1> 	at org.elasticsearch.test.InternalTestCluster.getMasterName(InternalTestCluster.java:1913) ~[framework-7.0.0-SNAPSHOT.jar:7.0.0-SNAPSHOT]
14:52:15   1> 	at org.elasticsearch.test.InternalTestCluster.getMasterName(InternalTestCluster.java:1902) ~[framework-7.0.0-SNAPSHOT.jar:7.0.0-SNAPSHOT]
14:52:15   1> 	at org.elasticsearch.test.InternalTestCluster.nonMasterClient(InternalTestCluster.java:776) ~[framework-7.0.0-SNAPSHOT.jar:7.0.0-SNAPSHOT]
14:52:15   1> 	at org.elasticsearch.cluster.SpecificMasterNodesIT.lambda$testElectOnlyBetweenMasterNodes$0(SpecificMasterNodesIT.java:122) ~[test/:?]
14:52:15   1> 	at org.elasticsearch.test.ESTestCase.assertBusy(ESTestCase.java:846) [framework-7.0.0-SNAPSHOT.jar:7.0.0-SNAPSHOT]

But there are also several earlier connection Exceptions like:

14:52:14   1> Caused by: java.net.ConnectException: Connection refused

[elasticmachine]

Pinging @elastic/es-distributed

[cbuescher]

@ywelsch @DaveCTurner to mute or not to mute? 💀

[ywelsch]

mute :)

[cbuescher]

Muted on master with 5ee7232.