Add support for delta OTA

 Put images to "old" dir for apply delta OTA

update_payload/applier.py

@@ -394,9 +394,9 @@ def _ApplyDiffOperation(self, op, op_name, patch_data, old_part_file,
           data_length=op.dst_length if op.dst_length else
           self._BytesInExtents(op.dst_extents, "%s.dst_extents"))
 
-      new_file_name = '/dev/fd/%d' % new_part_file.fileno()
+      new_file_name = new_part_file.name
       # Diff from source partition.
-      old_file_name = '/dev/fd/%d' % old_part_file.fileno()
+      old_file_name = old_part_file.name
 
       # In python3, file descriptors(fd) are not passed to child processes by
       # default. To pass the fds to the child processes, we need to set the flag