Error when running `cargo run` without passing config

```bash
called `Result::unwrap()` on an `Err` value: LedgerIsMissingValidatorKeypair("/var/folders/b0/0tqgzp3j0vv0y_0cb8shvg940000gn/T/.tmpff5wXH/validator-keypair.json")
```

We should do instead:
- If VALIDATOR_IDENTITY exists always create the validator_keypair.json and faucet.json
- If not defined, create a random one