dispatchResponse

Feed one already-parsed inbound message to the waiter table. Returns true if it was a response/error that matched a live transaction id (and so was consumed here), and false otherwise. On false the caller (DhtNode) should treat it as an inbound query, or as a stray or late reply, and handle it itself.

Port of the response branch of rpc_manager::incoming: look the id up, and if a waiter exists complete it (or, for y:"e", fail it with a DhtProtocolException). A response whose id is not in the table is a late/duplicate reply and is dropped (return false; libtorrent logs "unknown transaction id").