remove process_results item from rpc requests

[ripienaar]

Long ago we optimised the fire and forget style requests - where the client does not care for any results - by setting process_results to false/true and ensure its always in the request.

While a valid optimisation the baggage of carrying this key everywhere and remembering to handle it all the time etc is just too much for the minimal improvement in resource use it would result in for this hardly ever used pattern.

So we should kill it all, process_results should never get into any request.

See choria-legacy/mcorpc-agent-provider#126 for an example of the kind of pain this is causing, its so easy to forget its there since it seems it should be handled at a higher layer not wedged into this object.