GC Docker containers and images after the container exits

[diptanu]

Fixes #973

[sheerun]

How does it relate to following? Are logs still kept?

The idea behind keeping the allocations after they have completed for some time is to allow users to inspect the allocation once they have finished in case they want to debug something.

[dadgar]

@sheerun They are unrelated. This is about cleaning up the container which is managed by docker while logs are managed by us.

[diptanu]

@sheerun Yes, like @dadgar said logs would still be retained as they live in the allocation directory and we don't ask Docker to remove the volumes when we remove the container.

[dadgar]

Remove debug print

[github-actions]

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