The debug_work_activate() is called on the premise that
the work can be inserted, because if wq be in WQ_DRAINING
status, insert work may be failed.

Fixes: e41e704b ("workqueue: improve destroy_workqueue() debuggability")
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>