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/fifo.go

@@ -34,7 +34,8 @@ type ErrRequeue struct {
 	Err error
 }
 
-var FIFOClosedError error = errors.New("DeltaFIFO: manipulating with closed queue")
+// ErrFIFOClosed used when FIFO is closed
+var ErrFIFOClosed = errors.New("DeltaFIFO: manipulating with closed queue")
 
 func (e ErrRequeue) Error() string {
 	if e.Err == nil {
@@ -66,7 +67,7 @@ type Queue interface {
 	Close()
 }
 
-// Helper function for popping from Queue.
+// Pop is helper function for popping from Queue.
 // WARNING: Do NOT use this function in non-test code to avoid races
 // unless you really really really really know what you are doing.
 func Pop(queue Queue) interface{} {
@@ -126,7 +127,7 @@ func (f *FIFO) Close() {
 	f.cond.Broadcast()
 }
 
-// Return true if an Add/Update/Delete/AddIfNotPresent are called first,
+// HasSynced returns true if an Add/Update/Delete/AddIfNotPresent are called first,
 // or an Update called first but the first batch of items inserted by Replace() has been popped
 func (f *FIFO) HasSynced() bool {
 	f.lock.Lock()
@@ -242,7 +243,7 @@ func (f *FIFO) GetByKey(key string) (item interface{}, exists bool, err error) {
 	return item, exists, nil
 }
 
-// Checks if the queue is closed
+// IsClosed checks if the queue is closed
 func (f *FIFO) IsClosed() bool {
 	f.closedLock.Lock()
 	defer f.closedLock.Unlock()
@@ -267,7 +268,7 @@ func (f *FIFO) Pop(process PopProcessFunc) (interface{}, error) {
 			// When Close() is called, the f.closed is set and the condition is broadcasted.
 			// Which causes this loop to continue and return from the Pop().
 			if f.IsClosed() {
-				return nil, FIFOClosedError
+				return nil, ErrFIFOClosed
 			}
 
 			f.cond.Wait()