Fix the monitoring contacts Slack Icinga urls for AWS
Fix the monitoring contacts Slack Icinga urls for AWS

The stackname is blue/green, whereas what we actually need is the AWS
environment name (production/staging).

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