Add correct production domains to router app
Add correct production domains to router app

Production doesn't follow the `*.{env}.marketplace.team` domain
pattern, so we need to set the domains explicitly.

This also scales router app to 3 instances from the production default
of 5. Nginx is pretty fast and additional instances would reduce cache
hits for any pages or assets cached by nginx.

alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws