Prevent kani crash during setup for first time

[jaisnan]

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By using the tar file as a lock mechanism, we can detect incomplete setups i.e when both kani's working directory and the tar file present before setup, we can simply use the local bundle to start setup again.

This still carries the minor risk that the setup getting interrupted (for the first time) while the tar file is being downloaded. In that case, we can inform the user about the broken tar extraction and ask them to restart the setup process.

Unfortunately, can't be tested automatically.

Resolves #1545

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