add iterate example for glist; improve variable name for ghttp.Server

container/glist/glist_example_test.go

@@ -69,7 +69,7 @@ func Example_iterate() {
 		return true
 	})
 	fmt.Println()
-	// iterate reading from head using IteratorDesc.
+	// iterate reading from tail using IteratorDesc.
 	l.IteratorDesc(func(e *glist.Element) bool {
 		fmt.Print(e.Value)
 		return true