Update vendored vault-unsealer to latest released version

[simonswine]

We are hard coding a commit for vault-unsealer. We should upgrade that to the latest released version.

https://github.com/jetstack/tarmak/blob/master/Gopkg.toml#L48

Also check if we are using the latest version in the terraform

Run a full cluster apply to verify the changes (no automated E2E yet)

[simonswine]

This is where you can find it in terraform: https://github.com/jetstack/tarmak/blob/master/terraform/amazon/vault/templates/vault_user_data.yaml#L304

[simonswine]

This has been fixed