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/apiserver/pkg/admission/initializer/initializer.go

@@ -17,7 +17,6 @@ limitations under the License.
 package initializer
 
 import (
-	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apiserver/pkg/admission"
 	"k8s.io/apiserver/pkg/authorization/authorizer"
 	"k8s.io/client-go/informers"
@@ -28,7 +27,6 @@ type pluginInitializer struct {
 	externalClient    kubernetes.Interface
 	externalInformers informers.SharedInformerFactory
 	authorizer        authorizer.Authorizer
-	scheme            *runtime.Scheme
 }
 
 // New creates an instance of admission plugins initializer.
@@ -37,13 +35,11 @@ func New(
 	extClientset kubernetes.Interface,
 	extInformers informers.SharedInformerFactory,
 	authz authorizer.Authorizer,
-	scheme *runtime.Scheme,
 ) pluginInitializer {
 	return pluginInitializer{
 		externalClient:    extClientset,
 		externalInformers: extInformers,
 		authorizer:        authz,
-		scheme:            scheme,
 	}
 }
 
@@ -61,10 +57,6 @@ func (i pluginInitializer) Initialize(plugin admission.Interface) {
 	if wants, ok := plugin.(WantsAuthorizer); ok {
 		wants.SetAuthorizer(i.authorizer)
 	}
-
-	if wants, ok := plugin.(WantsScheme); ok {
-		wants.SetScheme(i.scheme)
-	}
 }
 
 var _ admission.PluginInitializer = pluginInitializer{}