[HEAD-237] add default gateway option for passing to nodes. (missing export)
[HEAD-237] add default gateway option for passing to nodes. (missing export)

joyent/sdc-headnode,joyent/sdc-headnode,numericillustration/sdc-headnode,kaizengarden/sdc-headnode,joyent/sdc-headnode,kaizengarden/sdc-headnode,numericillustration/sdc-headnode,numericillustration/sdc-headnode,kaizengarden/sdc-headnode,kaizengarden/sdc-headnode,joyent/sdc-headnode