net: skip flaky TestLookupDotsWithRemoteSource on darwin

Updates golang/go#27992

Change-Id: Ic327df7cc5002a3d537f9117559c25f30e1eab9c
Reviewed-on: https://go-review.googlesource.com/c/151799
Run-TryBot: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/lookup_test.go

@@ -618,6 +618,9 @@ func TestLookupDotsWithLocalSource(t *testing.T) {
 }
 
 func TestLookupDotsWithRemoteSource(t *testing.T) {
+	if runtime.GOOS == "darwin" {
+		testenv.SkipFlaky(t, 27992)
+	}
 	mustHaveExternalNetwork(t)
 
 	if !supportsIPv4() || !*testIPv4 {