net: disable dualstack listener tests on dragonfly

Change-Id: Ia7914156e4369113dea7c17b3aa51096e25f1901
Reviewed-on: https://go-review.googlesource.com/10834Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/net/listen_test.go

@@ -218,7 +218,7 @@ var dualStackTCPListenerTests = []struct {
 // listening address and same port.
 func TestDualStackTCPListener(t *testing.T) {
 	switch runtime.GOOS {
-	case "nacl", "plan9":
+	case "dragonfly", "nacl", "plan9": // re-enable on dragonfly once the new IP control block management has landed
 		t.Skipf("not supported on %s", runtime.GOOS)
 	}
 	if !supportsIPv4 || !supportsIPv6 {
@@ -305,7 +305,7 @@ var dualStackUDPListenerTests = []struct {
 // listening address and same port.
 func TestDualStackUDPListener(t *testing.T) {
 	switch runtime.GOOS {
-	case "nacl", "plan9":
+	case "dragonfly", "nacl", "plan9": // re-enable on dragonfly once the new IP control block management has landed
 		t.Skipf("not supported on %s", runtime.GOOS)
 	}
 	if !supportsIPv4 || !supportsIPv6 {