LU-4923 lfsck: detailed statistics for namespace LFSCK

LU-4923 lfsck: detailed statistics for namespace LFSCK

Some enhancement for namespace LFSCK:

1) For the MDT device upgraded from Lustre-1.x and still not enable
   the 'dirdata' feature, then send warning message when mount.

2) More detailed statistics for how many FID-in-dirent entries have
   been repaired and how many linkEA entries have been repaired.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I6a2468b1b8ac4dee91d5d3a26872214391fd3e3b
Reviewed-on: http://review.whamcloud.com/10030
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>