[#50887571] Call es::local_proxy on s_backend
[#50887571] Call es::local_proxy on s_backend

Forwards to the three ES nodes. We could pull these hostnames out to
extdata for more flexibility.

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