For everyday developer use, we don't need volumes for testing CSI. Providing a
flag to opt-in speeds up deploying dev clusters and slightly reduces infra costs.
Skip CSI test if missing volume specs.
Provisions vault with the policies described in the Nomad Vault integration
guide, and drops a configuration file for Nomad vault server configuration
with its token. The vault root token is exposed to the E2E runner so that
tests can write additional policies to vault.
This changeset adds volumes but does not mount them to instances so
that we can test the mounting ("staging") via CSI plugins. The CSI
plugins themselves will be installed as Nomad jobs.
In order to ensure we can always mount the EFS volume, this changeset
pins the deployment of the cluster to a specific subnet. In future
work we should spread the cluster out among several AZs and test that
behavior explicitly.
