Add Sidekiq alerting thresholds as ENV vars.
Add Sidekiq alerting thresholds as ENV vars.

For this application we expose Sidekiq stats in
the `/healtcheck` endpoint which decides on status
based on configuration, which should be set as ENV
vars, like a good 12facter application. Puppet is
not the ideal place for these but it’s what we do
everywhere else.

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