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/api/resource/math.go

@@ -194,9 +194,9 @@ func negativeScaleInt64(base int64, scale Scale) (result int64, exact bool) {
 	}
 	if fraction {
 		if base > 0 {
-			value += 1
+			value++
 		} else {
-			value += -1
+			value--
 		}
 	}
 	return value, !fraction