ModelControllerClientOperationHandler.ExecuteRequestHandler has special logic for the ":reload" op such that once the operation notifies that it is prepared, it immediately sends the final "success" result to the client, not waiting for the op execution to return to send it. This allows the response to go out to the client before the reload starts shutting down services.

A ":shutdown" op has similar effects to a ":reload" so there is no reason to treat it differently.

(Note: This special handling of ":reload" isn't a perfect thing, as it only covers the direct use of the ":reload" op. It doesn't cover things like a reload as a step in a composite. For the composite case, we need to give the step handlers for the other steps a chance to run any ResultHandlers they have registered and fix up the response before we send it back, so we can't just ignore that part of the execution.)