Create /run/udev/rules.d before using it since nothing else is creating it for us

http://bugs.gentoo.org/453656

--- init.d/udev
+++ init.d/udev
@@ -118,7 +118,9 @@
 {
 	if is_service_enabled network; then
 		# disable network hotplugging
-		local f="/run/udev/rules.d/90-network.rules"
+		local d="/run/udev/rules.d"
+		mkdir -p "${d}"
+		local f="${d}/90-network.rules"
 		echo "# This file disables network hotplug events calling" >> "${f}"
 		echo "# old-style openrc net scripts" >> "${f}"
 		echo "# as we use /etc/init.d/network to set up our network" >> "${f}"