use istio client-go library instead of knative (#1661)

use istio client-go library instead of knative
bump kubernetes dependency version
change code coverage to codecov

vendor/k8s.io/api/admissionregistration/v1/doc.go

@@ -0,0 +1,26 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// +k8s:deepcopy-gen=package
+// +k8s:protobuf-gen=package
+// +k8s:openapi-gen=true
+// +groupName=admissionregistration.k8s.io
+
+// Package v1 is the v1 version of the API.
+// AdmissionConfiguration and AdmissionPluginConfiguration are legacy static admission plugin configuration
+// MutatingWebhookConfiguration and ValidatingWebhookConfiguration are for the
+// new dynamic admission controller configuration.
+package v1 // import "k8s.io/api/admissionregistration/v1"