Add logstash nodes and elasticsearch to cacti.

* modules/openstack_project/manifests/cacti.pp: Add
logstash-worker[123].o.o and elasticsearch.o.o to the list of hosts
monitored by cacti.

Change-Id: Icfe658e6b6b097b61ae6753acee9a690c4076275
Reviewed-on: https://review.openstack.org/30926
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Elizabeth Krumbach Joseph <lyz@princessleia.com>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins