coverity: closedir on error path

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>

src/lxc/lxccontainer.c

@@ -2538,6 +2538,10 @@ static int lxcapi_snapshot_list(struct lxc_container *c, struct lxc_snapshot **r
 			lxcsnap_free(&snaps[i]);
 		free(snaps);
 	}
+	process_lock();
+	if (closedir(dir))
+		WARN("failed to close directory");
+	process_unlock();
 	return -1;
 }