LU-6482 lov: calculate file offset correctly

LU-6482 lov: calculate file offset correctly

In lov_stripe_pgoff(), it calls lov_stripe_size() to calculate the
file size by ost_size, which will be wrong if the stripe_index
happens to be stripe aligned.

Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Change-Id: I87f33027a835121e7b45687e3642ca50bfbf94da
Reviewed-on: http://review.whamcloud.com/14462
Tested-by: Maloo <hpdd-maloo@intel.com>
Tested-by: Jenkins
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>