LU-11697 osc: wrong page offset for T10PI checksum

LU-11697 osc: wrong page offset for T10PI checksum

The page offset might could be non-zero value. Thus, when
calculating T10PI checksum, the offset should be correct value.

Change-Id: Ib32584eb47ea55ec3804e531ac02ffd252411886
Signed-off-by: Li Xi <lixi@ddn.com>
Reviewed-on: https://review.whamcloud.com/33727
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Li Dongyang <dongyangli@ddn.com>
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>