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/apimachinery/pkg/util/sets/int.go

@@ -46,17 +46,19 @@ func IntKeySet(theMap interface{}) Int {
 }
 
 // Insert adds items to the set.
-func (s Int) Insert(items ...int) {
+func (s Int) Insert(items ...int) Int {
 	for _, item := range items {
 		s[item] = Empty{}
 	}
+	return s
 }
 
 // Delete removes all items from the set.
-func (s Int) Delete(items ...int) {
+func (s Int) Delete(items ...int) Int {
 	for _, item := range items {
 		delete(s, item)
 	}
+	return s
 }
 
 // Has returns true if and only if item is contained in the set.