Driver-Core: disable /sbin/hotplug by default

No recent mainstream system uses the /sbin/hotplug fork-bomb any more.
Disable it by default to reflect how it is used these days.

Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>