logstash: Increase shard replica count

Increase the shard replica count from 1 to 2 for new indices created
based on the logstash index template. This should help avoid data loss
in the case of a cluster split brain event at the cost of a 33% increase
in disk space utilization across the cluster. At current log volume and
index retention duration this should not be an issue.

This change has already been applied to the cluster and will take effect
on indices created on or after 2014-02-25.

Change-Id: I5e9fdde164eee27e43cac57ad56ad20ed04b1dae