Disable automatic index creation in Elasticsearch, fixes #618

When indexing documents in a non-existing index Elasticsearch will automatically
create that index by default (see http://www.elasticsearch.org/guide/en/elasticsearch/reference/0.90/docs-index_.html#index-creation)

This leads to the situation that the (Batched)ElasticSearchOutput will implicitly
create an index named like the deflector alias if it doesn't exist and hasn't been
(re-) created by DeflectorManagerThread.

By disabling the automatic index creation this race condition is prevented, although
the logs are being spammed with IndexMissingException messages from the Elasticsearch
outputs. Ideally the outputs would pause processing messages until the index and the
alias have been recreated and continue after a successful creation.