LUDOC-145 lfsck: enable FID-in-dirent before namespace LFSCK

LUDOC-145 lfsck: enable FID-in-dirent before namespace LFSCK

If the MDT is upgraded from Lustre software release 1.8, you
need to enable FID-in-dirent manually by "tune2fs -O dirdata".
Otherwise, the namespace LFSCK (since Lustre-2.4) will not
generate FID-in-dirent for the existing files.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: Ie562ce8aa2b336bf3afcdcea8f3ccdf396cb7502
Reviewed-on: https://review.whamcloud.com/26025
Tested-by: Jenkins
Reviewed-by: Joseph Gmitter <joseph.gmitter@intel.com>