Correct misnamed attribute from hostname to host
Correct misnamed attribute from hostname to host

I discovered this while running the app in production mode to check that
the smoke tests worked.

ministryofjustice/prison-visits-public,ministryofjustice/prison-visits-public,ministryofjustice/prison-visits-2,ministryofjustice/prison-visits-public,ministryofjustice/prison-visits-2,ministryofjustice/prison-visits-2,ministryofjustice/prison-visits-2,ministryofjustice/prison-visits-public