res/res_sorcery_astdb: Add a debugging message for when retrieval by ID fails

Having a debug message tell us that we attempted to look up an item but
failed is nice in circumstances when it isn't clear if the wizard was
queried correctly or not.

Change-Id: I2600c3bbea87f252196358f62e73f4c7da8632f7

res/res_sorcery_astdb.c

@@ -202,6 +202,7 @@ static void *sorcery_astdb_retrieve_id(const struct ast_sorcery *sorcery, void *
 	if (ast_db_get_allocated(family, id, &value) || !(json = ast_json_load_string(value, &error)) ||
 		!(objset = sorcery_json_to_objectset(json)) || !(object = ast_sorcery_alloc(sorcery, type, id)) ||
 		ast_sorcery_objectset_apply(sorcery, object, objset)) {
+		ast_debug(3, "Failed to retrieve object '%s' from astdb\n", id);
 		ao2_cleanup(object);
 		return NULL;
 	}