LU-1303 lod: transfer default striping from parent/fs

LU-1303 lod: transfer default striping from parent/fs

lod_ah_init() transfers default striping from the provided
parent if present or from filesystem defaults.
loaded/parsed default striping is cached in the parent.

Signed-off-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Change-Id: I575f2c2bddbf464c1eb93953b845ed563cfd081d
Reviewed-on: http://review.whamcloud.com/4054
Tested-by: Hudson
Reviewed-by: wangdi <di.wang@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>