LU-6030 ldiskfs: split pdirop patch

LU-6030 ldiskfs: split pdirop patch

Split pdirop patch as two parts. One for Nlevel-htree and Largedir,
other one for pdirop and htree-lock. Also doing some cleanup
work to reduce the patch size.

Signed-off-by: Yang Sheng <yang.sheng@intel.com>
Change-Id: I08b65d9098be95994f44748dbf14afa9f6d5b372
Reviewed-on: http://review.whamcloud.com/14264
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>