docker: add routing when shim network is used

etc/rc.d/rc.docker

@@ -500,8 +500,8 @@ stop_network(){
       TYPE=${NETWORK//[0-9.]/}
       if [[ $TYPE == br ]]; then
         LINK=shim-$NETWORK
-        GW=$(ip -4 route show default dev $NETWORK|awk '{print $3;exit}')
         if [[ -e $SYSTEM/$LINK ]]; then
+          GW=$(ip -4 route show default dev $NETWORK|awk '{print $3;exit}')
           [[ -n $GW ]] && ip -4 route del default via $GW dev $LINK
           ip addr flush dev $LINK
           ip link set $LINK down