Add ELASTICSEARCH_URI for rummager
Add ELASTICSEARCH_URI for rummager

Without setting this, it defaults to localhost (as per https://github.com/alphagov/rummager/blob/cbfe9ac6fbc1e3b55f37c57e948d71f02214afea/elasticsearch.yml).

In the old world, we used a local_proxy to the load balancing. In the
new world, we use ELBs and a DNS name.

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet