lightningd: derive JSONRPC ids from incoming id (append /cln:<method>#NNN).

Usually the calls are spontanous, so it's just "cln:<method>#NNN", but
json_invoice() calls listincoming, and json_checkmessage calls
listnodes, so those become "cli:invoice-<pid>/cln:listincoming#NNN".

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/invoice.c

@@ -1250,6 +1250,7 @@ static struct command_result *json_invoice(struct command *cmd,
 		info->b11->fallbacks = tal_steal(info->b11, fallback_scripts);
 
 	req = jsonrpc_request_start(info, "listincoming",
+				    cmd->id,
 				    cmd->ld->log,
 				    NULL, listincoming_done,
 				    info);