clean the hook lists

Make sure the hook lists are emptied so that the removed callbacks
are called. The callers should really remove the hook they installed
themselves but this is a last chance to fix things up.

src/tests/test-endpoint.c

@@ -239,6 +239,7 @@ endpoint_init(struct endpoint * self)
 static void
 endpoint_clear(struct endpoint * self)
 {
+	spa_hook_list_clean(&self->hooks);
 	pw_properties_free(self->properties);
 }