Add two more elasticsearch nodes.

* manifests/site.pp: List the two new elasticsearch nodes in the
appropriate lists.

* modules/logstash/manifests/elasticsearch.pp: Do not restart
elasticsearch when config files change. Service restarts are costly and
should be manually performed when necessary. Otherwise puppet should
simply update the config files.

* modules/logstash/templates/elasticsearch.yml.erb: Update elasticsearch
config with new cluster topology. Increase memory available for
indexing.

* modules/openstack_project/manifests/cacti.pp: Add new nodes to cacti
monitoring list.

Adding two more elasticsearch nodes to relieve memory pressure (more
nodes means fewer indexes per nodes which requires less memory to
manage). And two more nodes gives us more disk to retain older indexes
in. These new nodes should allow us to retain at least 3 weeks of
indexed logs.

Change-Id: I3a5a02311e939c8147e401110c7b96d085eb8274
Reviewed-on: https://review.openstack.org/36305
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins