Upgrade logstash and elasticsearch. Retune ES.

Upgrade logstash to 1.1.12. Upgrade elasticsearch to 0.20.5 (the version
corresponding to logstash 1.1.12). Go back to default elasticsearch
shard and replica counts.

Change-Id: I8e5497442e918f78677335ec29d03542c93734e5
Reviewed-on: https://review.openstack.org/29447
Reviewed-by: Elizabeth Krumbach Joseph <lyz@princessleia.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins