LU-8066 obd_type: discard obd_types linked list.

LU-8066 obd_type: discard obd_types linked list.

As all obd_types are kobjects in the lustre_kset kset,
they are linked together in that kset and don't
need any extra linkage.

There are non-obd_type objects in lustre_kset, added by
class_setup_tunables().  These have a different ->ktype, so we are
careful to only return objects with the correct ->ktype.

As kset_find_obj() returns a counted reference, we need
to put that reference when done.

On the server side it is possible to have an obd_type partially
initialized by one subsystem and latter fully initialized by
another subsystem. We use typ_sym_filter to notify us if the
obd_type is only partially setup. If it only paritially setup
then we let the original subsystem that created the obd_type
to clean it up. If the obd_type was latter completely setup
then we let the latter subsystem do the cleanup for us.

Linux-commit: 881bc9b58ef5e8c9be297b121187ea6c26572cf1

Change-Id: I4316644f7fb12e358b799af64deb57836e796066
Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-on: https://review.whamcloud.com/34718
Reviewed-by: Wang Shilong <wshilong@ddn.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Petros Koutoupis <pkoutoupis@cray.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Alexandr Boyko <c17825@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>