The `conn` here is `*winio.win32MessageBytePipe` which does not have a
`CloseRead` method (it does have `CloseWrite`) resulting in:
docker@WIN-NUC0 C:\Users\docker>.\docker-windows-amd64.exe system dial-stdio
the raw stream connection does not implement halfCloser
Also disable the path which uses this for cli-plugins on Windows.
Signed-off-by: Ian Campbell <ijc@docker.com>