Fix containerdisk doc
The Add command have to end with /
to copy into directory.
@@ -17,7 +17,7 @@ and upload to the container registry.
```
cat << END > Dockerfile
FROM scratch
-ADD fedora25.qcow2 /disk
+ADD fedora25.qcow2 /disk/
END
docker build -t vmdisks/fedora25:latest .
