01d2e16

Description:
After the PR #3851 (commit 01d2e16) we are not able to create Listeners from ADS on machines where IPv6 family is not enabled.

The error we get is
07:09:56 2018/07/19 14:09:56 Envoy STDERR: [2018-07-19 14:09:56.284][26][warning][upstream] source/common/config/grpc_mux_impl.cc:223] gRPC config for type.googleapis.com/envoy.api.v2.Listener update rejected: Error adding/updating listener testListener: IPv6 addresses are not supported on this machine: [::]:0

Repro steps:
Try to create Listener with ADS(any xDS) with the following Listener configuration. There is nothing special in the Listener configuration. Also please note that we are not using the new FilterMatch.

listener := v2.Listener{
		Name: "testListener",
		Address: core.Address{
			Address: &core.Address_SocketAddress{
				SocketAddress: &core.SocketAddress{
					Protocol: core.TCP,
					Address:  localhost,
					PortSpecifier: &core.SocketAddress_PortValue{
						PortValue: uint32(6666),
					},
				},
			},
		},
		FilterChains: []listener.FilterChain{{
			Filters: []listener.Filter{{
				Name:   util.HTTPConnectionManager,
				Config: managerStruct,
			}},
		}},
	}