Various kinds of decompressed streams are really ReadClosers. For instance gzip.NewReader() is, and the one returned from CmdStream is changed to be because it returns a PipeReader which is a ReadCloser. Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson) Upstream-commit: 0d9213f859e00459e9efee2c5164417c94d66d2f Component: engine