DeltaFIFO cleanup

Remove non-needed else condition
Remove non-needed swallow copy
Simplify return for IsClosed()
Keep amount decrement next to element extraction from the queue

Signed-off-by: Adrián Orive <adrian.orive.oneca@gmail.com>

staging/src/k8s.io/client-go/tools/cache/delta_fifo.go

@@ -320,17 +320,15 @@ func (f *DeltaFIFO) queueActionLocked(actionType DeltaType, obj interface{}) err
 	newDeltas := append(f.items[id], Delta{actionType, obj})
 	newDeltas = dedupDeltas(newDeltas)
 
-	_, exists := f.items[id]
 	if len(newDeltas) > 0 {
-		if !exists {
+		if _, exists := f.items[id]; !exists {
 			f.queue = append(f.queue, id)
 		}
 		f.items[id] = newDeltas
 		f.cond.Broadcast()
-	} else if exists {
-		// We need to remove this from our map (extra items
-		// in the queue are ignored if they are not in the
-		// map).
+	} else {
+		// We need to remove this from our map (extra items in the queue are
+		// ignored if they are not in the map).
 		delete(f.items, id)
 	}
 	return nil
@@ -348,9 +346,6 @@ func (f *DeltaFIFO) List() []interface{} {
 func (f *DeltaFIFO) listLocked() []interface{} {
 	list := make([]interface{}, 0, len(f.items))
 	for _, item := range f.items {
-		// Copy item's slice so operations on this slice
-		// won't interfere with the object we return.
-		item = copyDeltas(item)
 		list = append(list, item.Newest().Object)
 	}
 	return list
@@ -398,10 +393,7 @@ func (f *DeltaFIFO) GetByKey(key string) (item interface{}, exists bool, err err
 func (f *DeltaFIFO) IsClosed() bool {
 	f.closedLock.Lock()
 	defer f.closedLock.Unlock()
-	if f.closed {
-		return true
-	}
-	return false
+	return f.closed
 }
 
 // Pop blocks until an item is added to the queue, and then returns it.  If
@@ -432,10 +424,10 @@ func (f *DeltaFIFO) Pop(process PopProcessFunc) (interface{}, error) {
 		}
 		id := f.queue[0]
 		f.queue = f.queue[1:]
-		item, ok := f.items[id]
 		if f.initialPopulationCount > 0 {
 			f.initialPopulationCount--
 		}
+		item, ok := f.items[id]
 		if !ok {
 			// Item may have been deleted subsequently.
 			continue