LU-16369 ldiskfs: do not check enc context at lookup

LU-16369 ldiskfs: do not check enc context at lookup

On rhel8, ldiskfs should not check for encryption context of inodes
upon lookup. On these kernels, ext4 is not encryption aware, so just
assume context is fine when target is mounted as ldiskfs.

Lustre-change: https://review.whamcloud.com/49324
Lustre-commit: 540c293a4d0fc80253670b3db8d6722da43284ad

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I9f9813d290ea24b34f710e2c8219e856ca8fbc58
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Li Dongyang <dongyangli@ddn.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/49894
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>