Logged error message regarding kibana_task_manager index when starting Kibana and ES

[marius-dr]

Kibana version: 6.8.4

Original install method (e.g. download page, yum, from source, etc.): BC1

Describe the bug:
It's a shards failed message when starting ES and Kibana. Looks to be a race condition where the Task Manager tries to access the index before the cluster is out of RED. status.

Steps to reproduce:

1. Start Kibana.
2. Start ES.
3. Check ES logs

Provide logs and/or server output (if relevant):

[2019-10-21T16:12:08,840][INFO ][o.e.n.Node ] [5j5LCtM] started
[2019-10-21T16:12:08,891][DEBUG][o.e.a.s.TransportSearchAction] [5j5LCtM] All shards failed for phase: [query]
[2019-10-21T16:12:08,892][WARN ][r.suppressed ] [5j5LCtM] path: /.kibana_task_manager/_doc/_search, params: {ignore_unavailable=true, index=.kibana_task_manager, type=_doc}
org.elasticsearch.action.search.SearchPhaseExecutionException: all shards failed
at org.elasticsearch.action.search.AbstractSearchAsyncAction.onPhaseFailure(AbstractSearchAsyncAction.java:296) ~[elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.action.search.AbstractSearchAsyncAction.executeNextPhase(AbstractSearchAsyncAction.java:133) ~[elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.action.search.AbstractSearchAsyncAction.onPhaseDone(AbstractSearchAsyncAction.java:259) ~[elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.action.search.InitialSearchPhase.onShardFailure(InitialSearchPhase.java:100) ~[elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.action.search.InitialSearchPhase.lambda$performPhaseOnShard$1(InitialSearchPhase.java:208) ~[elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.action.search.InitialSearchPhase$1.doRun(InitialSearchPhase.java:187) [elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.common.util.concurrent.TimedRunnable.doRun(TimedRunnable.java:41) [elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:751) [elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-6.8.4.jar:6.8.4]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_201]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_201]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_201]
[2019-10-21T16:12:09,211][DEBUG][o.e.a.s.TransportSearchAction] [5j5LCtM] All shards failed for phase: [query]
[2019-10-21T16:12:09,211][WARN ][r.suppressed ] [5j5LCtM] path: /.kibana_task_manager/_doc/_search, params: {ignore_unavailable=true, index=.kibana_task_manager, type=_doc}
org.elasticsearch.action.search.SearchPhaseExecutionException: all shards failed
at org.elasticsearch.action.search.AbstractSearchAsyncAction.onPhaseFailure(AbstractSearchAsyncAction.java:296) ~[elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.action.search.AbstractSearchAsyncAction.executeNextPhase(AbstractSearchAsyncAction.java:133) ~[elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.action.search.AbstractSearchAsyncAction.onPhaseDone(AbstractSearchAsyncAction.java:259) ~[elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.action.search.InitialSearchPhase.onShardFailure(InitialSearchPhase.java:100) ~[elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.action.search.InitialSearchPhase.lambda$performPhaseOnShard$1(InitialSearchPhase.java:208) ~[elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.action.search.InitialSearchPhase$1.doRun(InitialSearchPhase.java:187) [elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.common.util.concurrent.TimedRunnable.doRun(TimedRunnable.java:41) [elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:751) [elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-6.8.4.jar:6.8.4]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_201]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_201]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_201]
[2019-10-21T16:12:09,276][INFO ][o.e.c.r.a.AllocationService] [5j5LCtM] Cluster health status changed from [RED] to [GREEN] (reason: [shards started [[.kibana_1][0]] ...]).

It doesn't happen on the other 2 releases: 7.4.1 an 7.5.0