[CI] CoordinationStateTests testSafety failure

[cbuescher]

Failed on 7.6 here: https://gradle-enterprise.elastic.co/s/xqj6qfl7477mk

This reproduces on 7.6, and also tried on 7.x and master where it also failed for me locally:

./gradlew ':server:test' --tests "org.elasticsearch.cluster.coordination.CoordinationStateTests.testSafety" \
  -Dtests.seed=C09AD7BDD00AAC7B \
  -Dtests.security.manager=true \
  -Dtests.locale=ar \
  -Dtests.timezone=America/Mendoza

java.lang.AssertionError: Multiple masters [{node_0}{0NdpewAAQACzD8aQ_____w}{0.0.0.0}{0.0.0.0:108}{dim}, {node_0}{BpeDEGvzSDacDK6h3VlWeA}{0.0.0.0}{0.0.0.0:108}{dim}] for term 1
Expected: a collection with size <1>
     but: collection size was <2>
	at __randomizedtesting.SeedInfo.seed([C09AD7BDD00AAC7B:F6B17BEDE9B8F0AB]:0)
	at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:18)
	at org.junit.Assert.assertThat(Assert.java:956)
	at org.elasticsearch.cluster.coordination.CoordinationStateTestCluster.lambda$invariant$10(CoordinationStateTestCluster.java:262)
	at java.util.HashMap.forEach(HashMap.java:1289)
	at org.elasticsearch.cluster.coordination.CoordinationStateTestCluster.invariant(CoordinationStateTestCluster.java:260)
	at org.elasticsearch.cluster.coordination.CoordinationStateTestCluster.runRandomly(CoordinationStateTestCluster.java:253)
	at org.elasticsearch.cluster.coordination.CoordinationStateTests.testSafety(CoordinationStateTests.java:777)

[elasticmachine]

Pinging @elastic/es-distributed (:Distributed/Distributed)