staging/lustre/osc: get rid of old checksum initial value

Old code residue assumes initial checksum value as ~0, and relies on
that to check whether OST server has calculated bulk data checksum.
That is not the case anymore.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Reviewed-on: http://review.whamcloud.com/10354
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4937


Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>