If a task was in a stopped state before we started to ptrace-seize
it, this stopped state will be restored by kernel upon detach.

If SIGSTOP was only in a task queue, we need to send it by hands
again bedore detaching. Otherwise we clean stop from queue (to
run parasite) and seize will restore task as running.

And, since SIGSTOP doesn't affect states of already stopped tasks,
we can send it to then safely and not distinguish stopped from
stop-queued ones.

Reported-by: Mr Jenkins
Signed-off-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>