Switch unicorn application server to use port 3000
Switch unicorn application server to use port 3000

This MUST be combined with a change to the
host (nginx) to container port mapping, defined
in your deployment.

For Template-deploy this goes in [enviroment specific pillar file](https://github.com/ministryofjustice/template-deploy/blob/master/pillar/prod/prod.sls).

A CCCD Template-deploy specific example can be
[found on this line](https://github.com/ministryofjustice/advocate-defence-payments-deploy/blob/master/pillar/demo/demo.sls#L52)

ministryofjustice/advocate-defence-payments,ministryofjustice/advocate-defence-payments,ministryofjustice/advocate-defence-payments,ministryofjustice/advocate-defence-payments