LU-14734 ldiskfs: improve message for large_dir

LU-14734 ldiskfs: improve message for large_dir

Make it more clear that the large_dir feature has already been
enabled, rather than making the admin think that they need to
enable the feature themselves.

Test-Parameters: trivial
Fixes: f5967b06aac5 ("LU-14734 osd-ldiskfs: enable large_dir automatically")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ica59d3370148ed277d3541c05be065c4638daf8d
Reviewed-on: https://review.whamcloud.com/45046
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>