dbus: Cancelling a service request always reply by an error

p2p_sd_cancel_request returns -1 in case of error, so does
wpas_p2p_sd_cancel_request.

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>

wpa_supplicant/dbus/dbus_new_handlers_p2p.c

@@ -2415,7 +2415,7 @@ DBusMessage * wpas_dbus_handler_p2p_service_sd_cancel_req(
 	if (req == 0)
 		goto error;
 
-	if (!wpas_p2p_sd_cancel_request(wpa_s, req))
+	if (wpas_p2p_sd_cancel_request(wpa_s, req) < 0)
 		goto error;
 
 	return NULL;