Vendor after merging containers/image#436

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/github.com/containers/storage/drivers/chroot_windows.go

@@ -0,0 +1,15 @@
+package graphdriver
+
+import (
+	"os"
+	"syscall"
+)
+
+// chrootOrChdir() is either a chdir() to the specified path, or a chroot() to the
+// specified path followed by chdir() to the new root directory
+func chrootOrChdir(path string) error {
+	if err := syscall.Chdir(path); err != nil {
+		return fmt.Errorf("error changing to %q: %v", path, err)
+	}
+	return nil
+}