LU-16634 misc: standardize iocontrol param handling

LU-16634 misc: standardize iocontrol param handling

Validate uarg and karg early in iocontrol processing where needed.
This needs kernel interop for 4.20+ kernels for access_ok(), but
this can be checked by #ifdef and does not need an autoconf test.

Fix incorrect definition of OBD_IOC_BARRIER to match reality.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Reported-by: Tao Lyu <tao.lyu@epfl.ch>
Change-Id: I1a0d2f839949debf346aa15c65b0f407e9ce7057
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50314
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Vitaliy Kuznetsov <vkuznetsov@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>