LU-15850 llite: pass dmv inherit depth instead of dir depth

LU-15850 llite: pass dmv inherit depth instead of dir depth

In directory creation, once it's ancestor has default LMV, pass
the inherit depth, otherwise pass the directory depth to ROOT.

This depth will be used in QoS allocation.

Lustre-change: https://review.whamcloud.com/47577
Lustre-commit: c23c68a52a04369101db2bd3b1d3da23025fcf48

Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: Id480f32c1718e9f62314c2dfe8905be5db94d1f2
Reviewed-on: https://review.whamcloud.com/47870
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>