[Virtio-fs] [virtiofsd] Issue opened: Change options defaults

This list compiles some proposed changes from default values.

Make default:
- [] `--inode-files-handles=fallback`
We could also take the opportunity to take a look at #20 deprecating `fallback` and changing it to: `best-effort`, `prefer`, `preferred`, etc.

- [] `--announce-submounts`


- [] `--no-killpriv-v2`


If you think there's something missing here, please add it.
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https://gitlab.com/virtio-fs/virtiofsd/-/issues/35