Better support for multiple nodes via ./gradlew run

[jakelandis]

This commit makes minor changes to support multiple nodes
via ./gradlew run. The specific desired use case, where there 2 nodes
in the cluster where one is a coordinating only node is used as
the example configuration.

[elasticsearchmachine]

Pinging @elastic/es-delivery (Team:Delivery)

[mark-vieira]

I'm confused why we don't use the same approach as for CCS, where you simply configure a test cluster with however many nodes and with whatever config you want, then just instruct the runtask to use that cluster?

[jakelandis]

I'm confused why we don't use the same approach as for CCS

Indeed. I noticed that too when working on this and am testing a change to make run-ccs look like this and will likely submit a PR to use this approach for run-css. The missing piece was the cluster.restart() to update the on-disk configuration before start.

[jakelandis]

@mark-vieira - ready for another round of review/discussion. thanks !

[jakelandis]

@elasticsearchmachine run elasticsearch-ci/packaging-tests-windows-sample

[jakelandis]

@elasticsearchmachine update branch

[jakelandis]

@elasticmachine update branch