Add k8s tags to related tests (#1018)

, so that `make test` will pass by default.

Also fixed several ineffassign and golint issues.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

middleware/kubernetes/federation.go

@@ -30,6 +30,9 @@ func (k *Kubernetes) Federations(state request.Request, fname, fzone string) (ms
 		return msg.Service{}, err
 	}
 	r, err := parseRequest(state)
+	if err != nil {
+		return msg.Service{}, err
+	}
 
 	lz := node.Labels[LabelZone]
 	lr := node.Labels[LabelRegion]