LU-6142 lov: convert container_of0() calls.

LU-6142 lov: convert container_of0() calls.

Most calls to container_of0() in lustre/lov/ are preceded by an
LINVRNT() which assures us that the pointer is valid, so
container_of() can be used instead.

Only in lov2obd() is there not context, so that call is changed to use
container_of_safe()

Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I8b3ccc8f0ac1a32122f043e8feec078fcfe2452b
Reviewed-on: https://review.whamcloud.com/38382
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Arshad Hussain <arshad.super@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>