Add image-volume local cache to speed up image volume creation

Although OpenStack Block Storage has an optional Image cache which can dramatically improve the performance of creating a volume from an image. The improvement depends on many factors, primarily how quickly the configured back end can clone a volume. But if clone is not supported by the back end or users did not buy this clone feature. And even worse, cinder and glance were not deployed in the same location. Then create volume from image will depend on the network performance between cinder and glance. So, If cloning cannot be used , can we cache the image to the cinder node when first create volume? This saves the download time when you create volume with the same image later.