API Catalog reports internal hostname (gateway-service) in Swagger

[markjhollands]

In the API Catalog, when you explore an API (for example the API mediation layer API) the servers used for "Try It Out" shows the internal hostname for the gateway service... i.e. the hostname used by the Docker / Kubernetes network. This means a client cannot access it.

We may just need to set the correct environment variable for the external hostname.