image: generate useful config

[cyphar]

The previous config generation produced a config which would cause runC to run the container using the host filesystem (with no namespaces set up). While we should try to be as agnostic as possible, we don't want to generate config.json payloads that are known to be bad (and useless).

Fixes #76

Signed-off-by: Aleksa Sarai [email protected]

[coolljt0725]

I'm +1 with this

[vbatts]

I'm +1 for this, but it looks like make lint is failing.

[zhouhao3]

@cyphar I passed the test after I rebased it. Can you rebase it?