x-forwarded-port makes little sense

Given that I have an API gateway set up like this: `wsk api create /base /test GET test -n testapi --response-type http`, then I can access it like this:

```
$ curl https://service.eu.apiconnect.ibmcloud.com/gws/apigateway/api/2fb...be1/base/test
```

Inspecting `__ow_headers`, I find this:
```
"x-forwarded-url": "https://service.eu.apiconnect.ibmcloud.com/gws/apigateway/api/2fb...be1/base/test",
"x-forwarded-port": "8080",
```

The URL is correct, but the port should be `443`.

Start by reproducing the API gateway request with the shown curl command and inspect __ow_headers, focusing on how x-forwarded-port is generated alongside x-forwarded-url. Done means an HTTPS request through the gateway reports port 443 instead of 8080 while preserving the correct forwarded URL.

Written by the indexing model from the issue text.