Auto migration server should not expose an http server (breaks deployments on Render.com)

I'm using the auto migrations image `FROM hasura/graphql-engine:v1.1.0-beta.3.cli-migrations`.

I'm having lots of problems deploying to Render.com because they automatically detect the open http port and expose that to the internet.

What's happening is they detect the temporary migration port and expose that. Then the migration server shuts down and my app isn't accessible to the internet.

The current behavior seems "hacky". Is there anyway it can be changed to not expose any http server while doing migrations?

My current workaround is set `HASURA_GRAPHQL_MIGRATIONS_SERVER_PORT=8080` so they detect the correct port, but now I loose zero-downtime deployments because /healthz returns OK while migrations are in progress.