LU-13054 ldiskfs: split htree_lock as separate patch

LU-13054 ldiskfs: split htree_lock as separate patch

The htree_lock part is identical in the different
distro version of pdirop patch. So move it out as
separate patch to reduce maintenance effort.

Signed-off-by: Yang Sheng <ys@whamcloud.com>
Change-Id: I423cc957de37ccdb097c9893f69481ce947ac78c
Reviewed-on: https://review.whamcloud.com/38372
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>