LU-3943 utils: fix lfs df -i summary line

LU-3943 utils: fix lfs df -i summary line

If the number of free objects on the OSTs is fewer than on the MDT,
use the number of free OST objects in the filesystem summary, so
it matches "df -i" (limited internally by ll_statfs_internal()).

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: Icfaaba3f9c39f12174e6681e9fb68c1f7a2540e5
Reviewed-on: http://review.whamcloud.com/8614
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Reviewed-by: Faccini Bruno <bruno.faccini@intel.com>
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>