sadc: Fix possible race condition in signal handler code

sadc: Fix possible race condition in signal handler code

Commit 1b52f939 tried to stop sending SIGINT to init process.
But there may be very small time window between parent ID
validation and sending kill signal to parent. If sar dies
during this window (though the chance is very small) we end up
sending signal to init.

This patch fixes above issue.

Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Sebastien GODARD <sysstat@users.noreply.github.com>