Ticket #3297: don't lose file in case of preallocate space fail.

Don't remove the destination file if it was retrieved incompletely
but it was already exist and appended during copy/move operation.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Merge branch '3297_preallocate_move_lose_data'

* 3297_preallocate_move_lose_data:
  Ticket #3297: don't lose file in case of preallocate space fail.