pulse-server: implement OBJECT_LINGER

Use OBJECT_LINGER in module-load to make sure the module stays loaded
after the client disconnects.
Implement linger in adapter and node-factory

src/modules/module-protocol-pulse/module.c

@@ -176,6 +176,7 @@ static int load_module(struct client *client, const char *name, const char *argu
 			pw_properties_set(props, "device.description", NULL);
 		}
 		pw_properties_set(props, "factory.name", "support.null-audio-sink");
+		pw_properties_set(props, PW_KEY_OBJECT_LINGER, "1");
 
 		module = calloc(1, sizeof(struct module));
 		module->client = client;