Switch to dedicated elasticsearch node.

Switch to a large dedicated elasticsearch node as sharing resources
between logstash, kibana, jenkins-log-pusher, and elasticsearch results
in a constrained environment.

Change-Id: I39e6210f2c577429be2cb38aca09111a0f56f9be
Reviewed-on: https://review.openstack.org/30344
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins