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/registry/generic/OWNERS

@@ -1,3 +1,5 @@
+# See the OWNERS docs at https://go.k8s.io/owners
+
 reviewers:
 - thockin
 - lavalamp
@@ -15,10 +17,8 @@ reviewers:
 - saad-ali
 - janetkuo
 - pwittrock
-- roberthbailey
 - ncdc
 - eparis
-- jlowdermilk
 - piosz
 - dims
 - hongchaodeng