Need way to tell libsoup "Response will not have body"

[Jens Georg <mail jensge org>]

In GUPnP, we have a request method called NOTIFY for unicast eventing. This is
called on a URI and has some headers and an XML body.

The response to this request is bodyless. We're using HTTP1.1 with keep-alive
here. Most clients include a Content-Length: 0 header in the response, but this
is not required by the standard.

If a client answers with just HTTP/1.1 200 OK and keeps the connection alive,
after receiving the headers, libsoup will wait for the body until a timeout
occurs, blocking the other messages queued in the SoupAsync session.

I've committed a work-around now that uses "Connection: close" in the original
request, but that makes us still fail if the client ignores that.

Is there any way to tell libsoup "There won't be a body, no need for waiting"?
I tried modifying the response header in "got-headers" or setting the encoding
before sending the message, but that didn't help