Enos buries the Terraform output from provisioning. Add a shell script to load
the environment from provisioning for debugging Nomad during development of
upgrade tests.
Add a README describing the setup required for running upgrade testing via
Enos. Also fix the authorization header of our `wget` to use the proper header
for short-lived tokens, and the output path variable of the artifactory step.
Co-authored-by: Juanadelacuesta <8647634+Juanadelacuesta@users.noreply.github.com>
