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/audit/util/conversion.go

@@ -35,6 +35,12 @@ func HookClientConfigForSink(a *v1alpha1.AuditSink) webhook.ClientConfig {
 			Name:      c.Service.Name,
 			Namespace: c.Service.Namespace,
 		}
+		if c.Service.Port != nil {
+			ret.Service.Port = *c.Service.Port
+		} else {
+			ret.Service.Port = 443
+		}
+
 		if c.Service.Path != nil {
 			ret.Service.Path = *c.Service.Path
 		}