[CI] CoreFullClusterRestartIT.testNewReplicasWork fails with security exception #30565
Description
https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+6.3+bwc-tests/49/console
19:44:18 ERROR 1.14s | CoreFullClusterRestartIT.testNewReplicasWork <<< FAILURES!
19:44:18 > Throwable #1: org.elasticsearch.client.ResponseException: method [POST], host [http://[::1]:46861], URI [/testnewreplicaswork/doc/159], status line [HTTP/1.1 403 Forbidden]
19:44:18 > {"error":{"root_cause":[{"type":"security_exception","reason":"action [indices:data/write/index[p]] is unauthorized for user [_system]"}],"type":"security_exception","reason":"action [indices:data/write/index[p]] is unauthorized for user [_system]"},"status":403}
19:44:18 > at __randomizedtesting.SeedInfo.seed([1A4895C4F873CE3C:60CC608FA07927E0]:0)
19:44:18 > at org.elasticsearch.client.RestClient$SyncResponseListener.get(RestClient.java:705)
19:44:18 > at org.elasticsearch.client.RestClient.performRequest(RestClient.java:235)
19:44:18 > at org.elasticsearch.client.RestClient.performRequest(RestClient.java:198)
19:44:18 > at org.elasticsearch.upgrades.FullClusterRestartIT.indexRandomDocuments(FullClusterRestartIT.java:1015)
19:44:18 > at org.elasticsearch.upgrades.FullClusterRestartIT.testNewReplicasWork(FullClusterRestartIT.java:206)
19:44:18 > at java.lang.Thread.run(Thread.java:748)