Prevent sm-notify from being run multiple times per reboot.

Prevent sm-notify from being run multiple times per reboot.

As "mount.nfs" can start statd, and as statd can start sm-notify,
the risk of sm-notify being run multiple times increases.
As this is not normally appropriate, sm-notify now creates a
file in /var/run which will stop future instances from being
run (though ofcourse this behaviour can be controlled by a
new command line option).