LU-16717 mdt: treat unknown hash type as sane type

LU-16717 mdt: treat unknown hash type as sane type

Directory migration failure may leave directory hash type as
LMV_HASH_TYPE_UNKNOWN|LMV_HASH_FLAG_BAD_TYPE, which should be treated
as sane hash type on existing directories, otherwise such directories
can't be unlinked.

Add sanity 230y.

Lustre-change: https://review.whamcloud.com/50796
Lustre-commit: 05cdb71ba6813570123613993f3cfcf74fc83561

Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: Ieffc0808d1db989d0bf9723f05cddb06f349e208
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/51202
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>