Only send a "routers" option if a default gateway is defined
Only send a "routers" option if a default gateway is defined

Currently, the "routers" DHCP option in always sent, but if the network has no
configured default gateway the option value is empty. Change this to check the
net.ip.gateway key, and only set the "routers" option is that key has a value.

notCalle/palletjack,creideiki/palletjack,notCalle/palletjack,creideiki/palletjack,saab-simc-admin/palletjack,saab-simc-admin/palletjack