restore: fix clean up in PIDNS

When processes are restored in PIDNS, the controll process (crtools)
don't know a real pid of processes, but it knows a pid of init.

crtools can kill init and all other processes will be killed too.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>