test: remap_dead_pid.c: Fix child PID not being printed

There's two issues with this code:

1. Child task is killed by parent faster, than it could print the line.
2. Even if it had time to print it - there would always be 0, because
it's called from child process.

Obviously, this print was meant to be in parent process. So, let's move
it there.

Signed-off-by: Vitaly Ostrosablin <vostrosablin@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>