[CI] VersionUtilsTests#testGradleVersionsMatchVersionUtils failure.

[martijnvg]

REPRODUCE WITH: gradle :test:framework:test -Dtests.seed=B5B94250EA246462 -Dtests.class=org.elasticsearch.test.VersionUtilsTests -Dtests.method="testGradleVersionsMatchVersionUtils" -Dtests.security.manager=true -Dtests.locale=sr-CS -Dtests.timezone=Asia/Jakarta
FAILURE 0.11s | VersionUtilsTests.testGradleVersionsMatchVersionUtils <<< FAILURES!
   > Throwable #1: java.lang.AssertionError: expected:<[6.0.0, 6.0.1, 6.1.0, 6.2.0]> but was:<[6.0.0, 6.0.1]>
   >    at __randomizedtesting.SeedInfo.seed([B5B94250EA246462:607A5855273429AC]:0)
   >    at org.elasticsearch.test.VersionUtilsTests.testGradleVersionsMatchVersionUtils(VersionUtilsTests.java:280)
   >    at java.lang.Thread.run(Thread.java:748)

This reproduces, but I don't know how to fix this.

The VersionUtils.allReleasedVersions() doesn't include 6.0.1 version, but tests.gradle_index_compat_versions list of versions does contain it. (based on indexCompatVersions variable in gradle). I think what VersionUtils.allReleasedVersions() is returning is correct, 6.0.1 has not been released yet, but this is not inline with indexCompatVersions.

[DaveCTurner]

Deeply related to #27397.

indexCompatVersions is what we test for index-compatibility against. Should we test master vs 6.0.1-SNAPSHOT? I think yes, until we're sure we're not going to release 6.0.1 (i.e. on release of 6.2.0.

[DaveCTurner]

Thanks @martijnvg, you beat me to it!