Further elasticsearch config tweaks.

* modules/logstash/files/elasticsearch.yml: Set the number of
elasticsearch shards to 1 and the number of replicas to 0 as we are
not running a cluster, just a single node.

* modules/openstack_project/manifests/logstash.pp: Update elasticsearch
indice optimization cron job's max_num_segments value from 1 to 2.

These options are suggested at
https://github.com/logstash/logstash/wiki/Elasticsearch-Storage-Optimization

Change-Id: I747ab8952f0102ba582e213407909aaeebcf2778
Reviewed-on: https://review.openstack.org/28616
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Khai Do <zaro0508@gmail.com>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins