pass spa_dict around as config

Don't pass pw_properties around when we simply need to pass around
config info, only use pw_properties when used to construct an object
that keeps the properties.

src/examples/export-spa.c

@@ -92,8 +92,10 @@ static int make_node(struct data *data)
 	}
 
 	data->proxy = pw_core_export(data->core,
-			SPA_TYPE_INTERFACE_Node, props,
+			SPA_TYPE_INTERFACE_Node, &props->dict,
 			data->node, 0);
+	pw_properties_free(props);
+
 	if (data->proxy == NULL)
 		return -errno;