We never ever close the stream so we do not need the Close() function in
th ebackend, the caller should close when required which may no be the
case, i.e. when os.Stdout/err is used.
This should not be a breaking change as the io.Writer is a subset of
io.WriteCloser, therfore all code should still compile while allowing to
pass in Writers without Close().
This is useful for podman top where we exec ps in the container via
podman exec.
Signed-off-by: Paul Holzinger <pholzing@redhat.com>