LU-8775 osd: do not report special writes in brw stats

LU-8775 osd: do not report special writes in brw stats

do not report special writes (e.g. last_rcvd, etc) made with
copying write in brw_stats.

Change-Id: Id92ed13a8d241e6489731d51a546c3583a2156b8
Signed-off-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-on: http://review.whamcloud.com/23363
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Zhiqi Tao <zhiqi.tao@intel.com>
Tested-by: Zhiqi Tao <zhiqi.tao@intel.com>
Tested-by: Jenkins
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>