[18.09 backport] image: do actual RootFS.DiffIDs copying in Clone() Upstream-commit: 423f39ab05d121e1aeb6e59732386fb50c17f49b Component: engine
[18.09 backport] image: do actual RootFS.DiffIDs copying in Clone() Upstream-commit: 423f39ab05d121e1aeb6e59732386fb50c17f49b Component: engine