ptp: add ipv6 support

* Wait for addresses to leave tentative state before setting routes
* Enable forwarding correctly
* Set up masquerading according to the active protocol

pkg/ipam/ipam.go

@@ -71,6 +71,8 @@ func ConfigureIface(ifName string, res *current.Result) error {
 		}
 	}
 
+	ip.SettleAddresses(ifName, 10)
+
 	for _, r := range res.Routes {
 		routeIsV4 := r.Dst.IP.To4() != nil
 		gw := r.GW