[Update] Update Jepsen from 0.2.3 to 0.2.4

What's the problem?

Jepsen 0.2.4 has been released but breaks backwards compatibility (perhaps unintentionally) with:

1) Username and Password based authentication.

2) No longer respects StrictHostKeyChecking being being disabled in the configuration.

This is because the upload and download functionality was delegated to launching scp as part of a sub-shell as opposed to the various ssh libraries it was using previously.

(See: usage of scp in jepsen).]

It's not easy to pass the username and password to scp which is why I imagine it was omitted.

But perhaps there's hope for making scp respect the disabling of StrictHostKeyChecking as this is much more trivial.

What's the fix?

1) We can dynamically generate a private key and public key pair, place it in the ./resources folder and make the public key available on the machines in the ./nodes file given that we know the username and password of the machines.

2) We can manually add an entry to the known_hosts file for each node.