[CI] IndexShardTests#testIndexCheckOnStartup fails

[jimczi]

https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+6.x+multijob-unix-compatibility/os=fedora/1268/console

Reproduce locally with:

./gradlew :server:test \
  -Dtests.seed=1DC5F9791FEAA886 \
  -Dtests.class=org.elasticsearch.index.shard.IndexShardTests \
  -Dtests.method="testIndexCheckOnStartup" \
  -Dtests.security.manager=true \
  -Dtests.locale=et \
  -Dtests.timezone=Pacific/Efate \
  -Dcompiler.java=10 \
  -Druntime.java=8

[elasticmachine]

Pinging @elastic/es-core-infra