The skip_unavailable setting did not exist until 6.1.0. This means that
we need to skip this test on versions prior to 6.1.0. We need to use
this setting because otherwise we will fail startup without it (since we
are not setting up a real remote cluster connection). This commit adds a
skip for all versions prior to 6.1.0.

* master: (24 commits)
  Only notify ready global checkpoint listeners (elastic#33690)
  Don't count hits via the collector if the hit count can be computed from index stats. (elastic#33701)
  Expose retries for CCR fetch failures (elastic#33694)
  Test fix - Graph vertices could appear in different orders based on map insertion sequence (elastic#33709)
  Structured audit logging (elastic#31931)
  Core: Add DateFormatter interface for java time parsing (elastic#33467)
  [CCR] Check whether the rejected execution exception has the shutdown flag set (elastic#33703)
  Mute ClusterDisruptionIT#testSendingShardFailure
  Revert "Mute FullClusterRestartSettingsUpgradeIT"
  Adjust BWC version on settings upgrade test (elastic#33650)
  [ML] Allow overrides for some file structure detection decisions (elastic#33630)
  Adapt skip version for doc_values format deprecation
  [TEST] wait for no initializing shards
  [Docs] Minor fix in `has_child` javadoc comment (elastic#33674)
  Mute FullClusterRestartSettingsUpgradeIT
  [Kerberos] Add realm name & UPN to user metadata (elastic#33338)
  [TESTS] Disable specific locales for RestrictedTrustManagerTest (elastic#33299)
  SQL: Return functions in JDBC driver metadata (elastic#33672)
  SCRIPTING: Move terms_set Context to its Own Class (elastic#33602)
  AwaitsFix testRestoreMinmal
  ...