Use check_app_health instead of check_nrpe
Use check_app_health instead of check_nrpe

This ensures that timeouts will cause `critical` alerts rather than
`unknown` alerts.

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