go.net/ipv6: update comment on multicast test
That's the reason why we now skip the test on freebsd.
R=dave
CC=golang-dev
https://golang.org/cl/10781043
diff --git a/ipv6/multicast_test.go b/ipv6/multicast_test.go
index 8bd6055..7267ad4 100644
--- a/ipv6/multicast_test.go
+++ b/ipv6/multicast_test.go
@@ -15,6 +15,7 @@
func TestPacketConnReadWriteMulticastUDP(t *testing.T) {
switch runtime.GOOS {
case "freebsd": // due to a bug on loopback marking
+ // See http://www.freebsd.org/cgi/query-pr.cgi?pr=180065.
t.Skipf("not supported on %q", runtime.GOOS)
case "plan9", "windows":
t.Skipf("not supported on %q", runtime.GOOS)
