Closed Issue: [WebApiOnOwin] Response sent in chunked encoding when it does not have any content [993]

When there is no content assigned to a HttpResponseMessage, the response is being sent in a chunked encoding format.

Example:
```
public HttpResponseMessage ReturnNoContent()
{
return Request.CreateResponse(HttpStatusCode.BadRequest);
}
```

__Attached__ a standalone repro.

Expected:
Has chunked encoding header?: __False__
Has chunked encoding header?: False
Has chunked encoding header?: False

Actual:
Has chunked encoding header?: __True__
Has chunked encoding header?: False
Has chunked encoding header?: False
Comments: Verified.