LU-13131 osc: remove redundant osc_list() helper

LU-13131 osc: remove redundant osc_list() helper

The osc_list() helper function is the same as list_empty_marker(),
and we don't need both.  Remove osc_list() from the code.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I07d2a519906f52fca8c95613a14ad7389a3ebbe5
Reviewed-on: https://review.whamcloud.com/37479
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Li Xi <lixi@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>