LU-2099 osd: set dr_elapsed before dr_numreqs

LU-2099 osd: set dr_elapsed before dr_numreqs

so that service thread always get dr_elapsed and
dr_elapsed_valid initialized when the bio is done.
also, the patch adds a bit of debug to help with
the original bug if this patch doesn't help.

Signed-off-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Change-Id: I7c41af9a2be5be2f37190fb053d7449653fc7a99
Reviewed-on: http://review.whamcloud.com/4216
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>