go.crypto/ssh: server_test should bind to localhost only

Hopefully fix build error under windows.

Binding to the wildcard is poor form for our darwin users
as it triggers the firewall popup. Dialing the wildcard
looks like it's implementation specific as well.

R=agl, kardianos
CC=golang-dev
https://golang.org/cl/6104046

ssh/server_test.go

@@ -120,7 +120,7 @@ func startSSHServer(t *testing.T) (addr string) {
 		t.Fatalf("Failed to parse private key: %s", err.Error())
 	}
 
-	listener, err := Listen("tcp", ":0", config)
+	listener, err := Listen("tcp", "127.0.0.1:0", config)
 	if err != nil {
 		t.Fatalf("Bind error: %s", err)
 	}