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/client-go/tools/cache/expiration_cache_fakes.go

@@ -33,16 +33,19 @@ func (c *fakeThreadSafeMap) Delete(key string) {
 	}
 }
 
+// FakeExpirationPolicy keeps the list for keys which never expires.
 type FakeExpirationPolicy struct {
 	NeverExpire     sets.String
 	RetrieveKeyFunc KeyFunc
 }
 
-func (p *FakeExpirationPolicy) IsExpired(obj *timestampedEntry) bool {
+// IsExpired used to check if object is expired.
+func (p *FakeExpirationPolicy) IsExpired(obj *TimestampedEntry) bool {
 	key, _ := p.RetrieveKeyFunc(obj)
 	return !p.NeverExpire.Has(key)
 }
 
+// NewFakeExpirationStore creates a new instance for the ExpirationCache.
 func NewFakeExpirationStore(keyFunc KeyFunc, deletedKeys chan<- string, expirationPolicy ExpirationPolicy, cacheClock clock.Clock) Store {
 	cacheStorage := NewThreadSafeStore(Indexers{}, Indices{})
 	return &ExpirationCache{