Work out the host and port for the container

Avoid docker inspect:
1. Use the container ID as the host
2. Configure the port, default to 3000

test/integration/docker/deployer/app_with_roles/config/deploy.yml

@@ -13,6 +13,7 @@ proxy:
   enabled: true
   hosts:
     - vm2
+  port: 80
   deploy_timeout: 2s
 
 asset_path: /usr/share/nginx/html/versions