Update FakeCli to remove duplication in tests.

Use byte buffers by default, since that is what is done most of the time.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

cli/command/stack/deploy_test.go

@@ -18,7 +18,7 @@ func TestPruneServices(t *testing.T) {
 		"keep": {},
 	}
 	client := &fakeClient{services: []string{objectName("foo", "keep"), objectName("foo", "remove")}}
-	dockerCli := test.NewFakeCli(client, &bytes.Buffer{})
+	dockerCli := test.NewFakeCliWithOutput(client, &bytes.Buffer{})
 	dockerCli.SetErr(&bytes.Buffer{})
 
 	pruneServices(ctx, dockerCli, namespace, services)