LUDOC-477 sec: fix kernel version for client encryption

LUDOC-477 sec: fix kernel version for client encryption

For distros explicitly listed in the doc, we use the embedded fscrypt
lib that we have copied and included in the Lustre source tree,
because these distros have not backported fscrypt v2.

Fixes: 1791cdb ("LUDOC-477 sec: doc for client-side encryption")
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I325438d29b765120aa58187730c33e08f8a8e340
Reviewed-on: https://review.whamcloud.com/41046
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>