Logstash: Configure Elasticsearch to automatically create indices

Configure the Elasticsearch cluster used for Logstash storage to allow
automatic creation of a new index when a document is stored under an
index that does not currently exist. Without this change we would have
to setup a cron job to explicitly create a new index each day.

This changeset adds a parameter to the elasticsearch class to control
the action.auto_create_index configuration setting and defaults it to
false to preserve the original class behavior.

Change-Id: I2c21b11d291875e7d30a7229eb1ba32f702146c5