LU-3335 scrub: convert filter_fid_old to LMA

LU-3335 scrub: convert filter_fid_old to LMA

The OI scrub will generate FID-in-LMA for old OST-object, which will
unify OSD behaviors. To make LMA to fit into the 256-byte OST inode,
it will shrink the filter_fid_old as filter_fid, and the parent FID
will be kept.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: Ife669f88b4657928abee774b089115d78b53c380
Reviewed-on: http://review.whamcloud.com/7143
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>