LU-3328 osp: Only signal thread completion when we are done

LU-3328 osp: Only signal thread completion when we are done

IT seems that by signalling the completion of a thread before
we are done inspecting it's memory is racy and could cause access
to freed memory.

Change-Id: Ia992e9c7d0d78fca1afbfc98f51c5df3f6dc3a28
Signed-off-by: Oleg Drokin <green@intel.com>
Reviewed-on: http://review.whamcloud.com/6329
Tested-by: Hudson
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>