Minor fix: let the result handler complete the request processing

Without this fix the example Proxy never returns responses to the client
application causing the client to hang indefinitely.

The proxy is asynchronous, so the client side response handler (emitter)
must be completed on completion of the proxied request. Before this
change the proxy would forward the request, then complete the response
handler, and only later receive the response to the proxied operation.
When it then tried to forward the results to the client it would
discover that the client's request had been cancelled.