LU-4952 osd: wrong paramters for dmu_tx_hold_write

LU-4952 osd: wrong paramters for dmu_tx_hold_write

osd_declare_write_commit may pass wrong parameters to
dmu_tx_hold_write when there are multiple IO fragments.

Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Change-Id: Ic7bd5ce1f42e7777c1a07eb4b9d19f8477da66a0
Reviewed-on: http://review.whamcloud.com/10079
Tested-by: Jenkins
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Isaac Huang <he.huang@intel.com>