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/sigs.k8s.io/controller-runtime/pkg/client/apiutil/apimachinery.go

@@ -14,6 +14,9 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+// Package apiutil contains utilities for working with raw Kubernetes
+// API machinery, such as creating RESTMappers and raw REST clients,
+// and extracting the GVK of an object.
 package apiutil
 
 import (
@@ -32,7 +35,10 @@ import (
 // information fetched by a new client with the given config.
 func NewDiscoveryRESTMapper(c *rest.Config) (meta.RESTMapper, error) {
 	// Get a mapper
-	dc := discovery.NewDiscoveryClientForConfigOrDie(c)
+	dc, err := discovery.NewDiscoveryClientForConfig(c)
+	if err != nil {
+		return nil, err
+	}
 	gr, err := restmapper.GetAPIGroupResources(dc)
 	if err != nil {
 		return nil, err
@@ -63,10 +69,13 @@ func GVKForObject(obj runtime.Object, scheme *runtime.Scheme) (schema.GroupVersi
 }
 
 // RESTClientForGVK constructs a new rest.Interface capable of accessing the resource associated
-// with the given GroupVersionKind.
+// with the given GroupVersionKind. The REST client will be configured to use the negotiated serializer from
+// baseConfig, if set, otherwise a default serializer will be set.
 func RESTClientForGVK(gvk schema.GroupVersionKind, baseConfig *rest.Config, codecs serializer.CodecFactory) (rest.Interface, error) {
 	cfg := createRestConfig(gvk, baseConfig)
-	cfg.NegotiatedSerializer = serializer.DirectCodecFactory{CodecFactory: codecs}
+	if cfg.NegotiatedSerializer == nil {
+		cfg.NegotiatedSerializer = serializer.WithoutConversionCodecFactory{CodecFactory: codecs}
+	}
 	return rest.RESTClientFor(cfg)
 }