ptrace: task_stopped_code(ptrace => true) can't see TASK_STOPPED task

ptrace: task_stopped_code(ptrace => true) can't see TASK_STOPPED task

task_stopped_code()->task_is_stopped_or_traced() doesn't look right, the
traced task must never be TASK_STOPPED.

We can not add WARN_ON(task_is_stopped(p)), but this is only because
do_wait() can race with PTRACE_ATTACH from another thread.

[[email protected]: teeny cleanup]
Signed-off-by: Oleg Nesterov <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Roland McGrath <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Cc: Pedro Alves <[email protected]>
Cc: Jan Kratochvil <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>