ci: add hostname in nats config
ci: add hostname in nats config

* now that cf-deployment uses nats-release v34 ([#172315755](https://www.pivotaltracker.com/story/show/172315755)), we need to configure this hostname since it is a required property now.

cloudfoundry-incubator/cf-networking-release,cloudfoundry-incubator/cf-networking-release,cloudfoundry-incubator/cf-networking-release,cloudfoundry-incubator/cf-networking-release