Context: Load-balancing in Exoscale is performed by associating many
workers with the same EIP. This works, however, the workers cannot access
themselves via the EIP, which is needed at least for cert-managers
"self-test".
Problem: The old iptables based workaround felt fragile and disappointed
me at least once.
New solution: Add the EIP to a loopback interface on each worker.
* contrib/terraform/exoscale: Rework SSH public keys
Exoscale has a few limitations with `exoscale_ssh_keypair` resources.
Creating several clusters with these scripts may lead to an error like:
```
Error: API error ParamError 431 (InvalidParameterValueException 4350): The key pair "lj-sc-ssh-key" already has this fingerprint
```
This patch reworks handling of SSH public keys. Specifically, we rely on
the more cloud-agnostic way of configuring SSH public keys via
`cloud-init`.
* contrib/terraform/exoscale: terraform fmt
* contrib/terraform/exoscale: Add terraform validate
* contrib/terraform/exoscale: Inline public SSH keys
The Terraform scripts need to install some SSH key, so that Kubespray
(i.e., the "Ansible part") can take over. Initially, we pointed the
Terraform scripts to `~/.ssh/id_rsa.pub`. This proved to be suboptimal:
Operators sharing responbility for a cluster risk unnecessarily replacing resources.
Therefore, it has been determined that it's best to inline the public
SSH keys. The chosen variable `ssh_public_keys` provides some uniformity
with `contrib/azurerm`.
* Fix Terraform Exoscale test
* Fix Terraform 0.14 test
