LU-4293 mdd: Allow layout swap for IGIF FIDs

LU-4293 mdd: Allow layout swap for IGIF FIDs

Patch to also allow layout swap for pre-2.x migrated
files (ie, IGIF FID with linkEA).

Root user special case has also been added to lfs/migrate
command to map owner/group of original file to
volatile, in order to comply with other layout_swap rules.

Lustre-commit: bd5ba50502bec5786c9a2f05c29f7b99a35147fb
Lustre-change: http://review.whamcloud.com/8737

Signed-off-by: Bruno Faccini <bruno.faccini@intel.com>
Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Change-Id: Iad6194c6050fa2ba066d2051871a10a60ddae995
Reviewed-on: http://review.whamcloud.com/9278
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>