ptrace: wait_consider_task: s/same_thread_group/ptrace_reparented/

wait_consider_task() checks same_thread_group(parent, real_parent),
this is the open-coded ptrace_reparented().

__ptrace_detach() remains the only function which has to check this by
hand, although we could reorganize the code to delay __ptrace_unlink.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>

kernel/exit.c

@@ -1599,8 +1599,7 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace,
 		 * own children, it should create a separate process which
 		 * takes the role of real parent.
 		 */
-		if (likely(!ptrace) && p->ptrace &&
-		    same_thread_group(p->parent, p->real_parent))
+		if (likely(!ptrace) && p->ptrace && !ptrace_reparented(p))
 			return 0;
 
 		/*