David Turner f864f6a740 Cluster state from API should always have a master (#42454)
Today the `TransportClusterStateAction` ignores the state passed by the
`TransportMasterNodeAction` and obtains its state from the cluster applier.
This might be inconsistent, showing a different node as the master or maybe
even having no master.

This change adjusts the action to use the passed-in state directly, and adds
tests showing that the state returned is consistent with our expectations even
if there is a concurrent master failover.

Fixes #38331
Relates #38432
2019-05-24 08:45:22 +01:00
..