Butler stream servers can generate client address.

logdog/client/butler/butler_test.go

Index: logdog/client/butler/butler_test.go
diff --git a/logdog/client/butler/butler_test.go b/logdog/client/butler/butler_test.go
index 1daa35310ab779a47fe77c4e9858efd602ab2668..50887ee9a70dcf2c281253c3a3d7d4eedd70fcf2 100644
--- a/logdog/client/butler/butler_test.go
+++ b/logdog/client/butler/butler_test.go
@@ -193,9 +193,9 @@ func newTestStreamServer() *testStreamServer {
 	}
 }
 
-func (tss *testStreamServer) Listen() error {
-	return tss.err
-}
+func (tss *testStreamServer) Address() string { return "test" }
+
+func (tss *testStreamServer) Listen() error { return tss.err }
 
 func (tss *testStreamServer) Next() (io.ReadCloser, *streamproto.Properties) {
 	if tss.onNext != nil {