LU-13241 utils: use libext2fs for ldiskfs operations

LU-13241 utils: use libext2fs for ldiskfs operations

Instead of using debugfs to stat and read the CONFIGS/mountdata,
we can switch to libext2fs and control the flags used when
opening the ldiskfs, to reduce the mount time on huge targets.

Change-Id: I9da8fc1c77d149fe5cf3bd19b0ff76d892620101
Signed-off-by: Li Dongyang <dongyangli@ddn.com>
Reviewed-on: https://review.whamcloud.com/37656
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Li Xi <lixi@ddn.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>