Stub forward/proxy tests (#108)

Test the handling of EDNS0 payloads and forwarding to stubzones
servers.

middleware/etcd/group_test.go

@@ -29,7 +29,7 @@ func TestGroupLookup(t *testing.T) {
 		_, err := etc.ServeDNS(ctx, rec, m)
 		if err != nil {
 			t.Errorf("expected no error, got %v\n", err)
-			return
+			continue
 		}
 		resp := rec.Msg()