LU-5916 lod: inherit default pool setting properly

LU-5916 lod: inherit default pool setting properly

When parent directory has no default striping but has only
default pool setting, the pool setting should be inherited
by subdir properly.

This patch fixed the problem by changing the
LOVEA_DELETE_VALUES() to check pool name as well, and it
removed the unused function lod_store_def_striping().

Lustre-commit: e8214d6bd4ccc3ff386c77904664c60f1848ef11
Lustre-change: http://review.whamcloud.com/#/c/12746/

Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Change-Id: I8ab9623772bb0d78965396daaab54353f07228f0
Reviewed-on: http://review.whamcloud.com/13411
Tested-by: Jenkins
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>