Invalid method returns 404 not 405

Given an API Gateway set up to only accept GET, if I try to POST to it, I get a `404` back.

I should get a [`405`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/405) as the resource exists (i.e. was found), but I'm not allowed to access it with this method.

```
$ wsk api create /hello / GET hello
ok: created API /hello/ GET for action /_/hello
https://service.eu.apiconnect.ibmcloud.com/gws/apigateway/api/d12...b12/hello/

$ curl -I -X POST https://service.eu.apiconnect.ibmcloud.com/gws/apigateway/api/d12..b12/hello
HTTP/1.1 404 Not Found
Access-Control-Allow-Methods: GET, POST, PUT, DELETE, PATCH, HEAD, OPTIONS
Access-Control-Allow-Origin: *
Content-Type: application/json; charset=utf-8
Date: Sun, 17 Sep 2017 19:07:37 GMT
Server: openresty
Content-Length: 62

{"status":404,"message":"Error: Whoops. Verb not supported."}
```