Remove windows code and simplify linux

Windows will not use containerd and its just unused code and unneed
complexity to keep it all around.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

ctr/container.go

@@ -621,3 +621,23 @@ type stdio struct {
 	stdout string
 	stderr string
 }
+
+func createStdio() (s stdio, err error) {
+	tmp, err := ioutil.TempDir("", "ctr-")
+	if err != nil {
+		return s, err
+	}
+	// create fifo's for the process
+	for name, fd := range map[string]*string{
+		"stdin":  &s.stdin,
+		"stdout": &s.stdout,
+		"stderr": &s.stderr,
+	} {
+		path := filepath.Join(tmp, name)
+		if err := syscall.Mkfifo(path, 0755); err != nil && !os.IsExist(err) {
+			return s, err
+		}
+		*fd = path
+	}
+	return s, nil
+}