LU-6750 zfs: add stop trans callback

LU-6750 zfs: add stop trans callback

Add stop transaction callback in OSD-ZFS, so when the
osd transaction is stopped, the top transaction
will be notified.

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: I56b8d964b3c4dd24e3c56429b7f1a8960d3202cb
Reviewed-on: http://review.whamcloud.com/15367
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>