Remove unnecessary `Container.changes` function.

Signed-off-by: David Calavera <david.calavera@gmail.com>

daemon/changes.go

@@ -9,5 +9,7 @@ func (daemon *Daemon) ContainerChanges(name string) ([]archive.Change, error) {
 		return nil, err
 	}
 
-	return container.changes()
+	container.Lock()
+	defer container.Unlock()
+	return daemon.changes(container)
 }

daemon/container.go

@@ -286,12 +286,6 @@ func (container *Container) Resize(h, w int) error {
 	return nil
 }
 
-func (container *Container) changes() ([]archive.Change, error) {
-	container.Lock()
-	defer container.Unlock()
-	return container.daemon.changes(container)
-}
-
 func (container *Container) getImage() (*image.Image, error) {
 	if container.daemon == nil {
 		return nil, derr.ErrorCodeImageUnregContainer