9p cache seems broken on alpine build

First of all, thanks a lot for this great project!

I have built the alpine 9p filesystem and the vm state using `build.sh` then `build-state.js` in `tools/docker/alpine/`. After loading them in the browser, each 9p file access generates a network (http) request so the cache=loose kernel parameter seems to be ignored.

Moreover, I don't know if it's related but the `mount` output contains the line

```
host9p on / type 9p (rw,relatime,cache=f,access=client,trans=virtio)
```

should it not be `cache=loose` (or `loose` alone, I don't know) ?

Just to mention that the 9p cache is working great when using `https://copy.sh/v86/?profile=archlinux` and `loose` appear in the 9p mount options.

Thanks for your help.