log: don't kill task, if unable to write pidfile

write_pidfile() was taken out from cr-restore.c, where it was supposed to kill
child if unable to create pidfile. Now we're also using it at service/page-server where kill is redundant. So lets take out kill() from write_pidfile() back to cr-restore.

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>