btrfs-progs: free path on read_chunk_tree error

Path allocation failure already has its own return, remember to free the
path when the error label is taken.

Signed-off-by: Zach Brown <zab@redhat.com>

volumes.c

@@ -1601,9 +1601,9 @@ again:
 		goto again;
 	}
 
-	btrfs_free_path(path);
 	ret = 0;
 error:
+	btrfs_free_path(path);
 	return ret;
 }