LU-6142 osd-ldiskfs: convert container_of0() to container_of()

LU-6142 osd-ldiskfs: convert container_of0() to container_of()

Every use of container_of0() in osd-ldiskfs can safely use
container_of() instead.  Doing so makes the intent of the code
clearer.

In most cases, the pointer returned is later dereferenced without any
subsequent checks.  In a few cases (e.g.  osd_obj()), the pointer
passed in is dereferenced before the container_of() call.  These
patterns assure us that the pointer in valid (not NULL or an ERR_PTR),
so container_of() is the correct interface to use.

Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I11cb51cd2dc459a3ab5c420ef7bf3324a28eeffc
Reviewed-on: https://review.whamcloud.com/38378
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>