LU-11850 obd: support target_obd using Netlink

LU-11850 obd: support target_obd using Netlink

Due to "target_obd" being an debugfs file normal users can't
access its contents. This breaks standard tools non-root.
Implement the same functionality using Netlink.

We don't implement it for lod since its an dt_device which
we don't have a way to find such a device like obd_devices.
The lod layer is server side so only root should have access.

Change-Id: I8fce80f6460b4b3f46106bc24d9494ae94e4fd4b
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58506
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>