wait_task_stopped: Check p->exit_state instead of TASK_TRACED

wait_task_stopped: Check p->exit_state instead of TASK_TRACED

The original meaning of the old test (p->state > TASK_STOPPED) was
"not dead", since it was before TASK_TRACED existed and before the
state/exit_state split.  It was a wrong correction in commit
14bf01bb0599c89fc7f426d20353b76e12555308 to make this test for
TASK_TRACED instead.  It should have been changed when TASK_TRACED
was introducted and again when exit_state was introduced.

Signed-off-by: Roland McGrath <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Kees Cook <[email protected]>
Acked-by: Scott James Remnant <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>