fngsystem:network:sharedconf: Reduce prio for route on static ip interfaces

Busybox ifup happens to setup a default route for interfaces with static ip adresses, also when no cable is connected. By default this route has higher priority then the route set by udhcp for an other interface, leading in a not working network setup. This reduces the prio ( sets a higher metric) for the static default route, so it is set, but overruled by a route set by udhcp.