Make container.Copy support volumes

Fixes #1992

Signed-off-by: Brian Goff <cpuguy83@gmail.com>
I don't like this change. This variable used only in `TarWithOptions` and without this change I saw that this is just `Compression` and `Includes`, now I need to look all code between this line and `TarWithOptions` to be sure that there is no other things in opts.