xnet/pipenet: Add tests for Host.Network

Should be in d3a7a196 (xnet/pipenet: Package for TCP-like synchronous
in-memory network of net.Pipes)

xnet/pipenet/pipenet_test.go

-// Copyright (C) 2017  Nexedi SA and Contributors.
+// Copyright (C) 2017-2018  Nexedi SA and Contributors.
 //                          Kirill Smelkov <kirr@nexedi.com>
 //
 // This program is free software: you can Use, Study, Modify and Redistribute
@@ -99,6 +99,9 @@ func TestPipeNet(t *testing.T) {
 	hα := pnet.Host("α")
 	hβ := pnet.Host("β")
 
+	assertEq(t, hα.Network(), "pipet")
+	assertEq(t, hβ.Network(), "pipet")
+
 	_, err := hα.Dial(context.Background(), ":0")
 	assertEq(t, err, &net.OpError{Op: "dial", Net: "pipet", Addr: xaddr("α:0"), Err: errConnRefused})