This changeset is part of the work to improve our E2E provisioning
process to allow our upgrade tests:
* Move more of the setup into the AMI image creation so it's a little
more obvious to provisioning config authors which bits are essential
to deploying a specific version of Nomad.
* Make the service file update do a systemd daemon-reload so that we
can update an already-running cluster with the same script we use to
deploy it initially.
Update the Consul and Vault configs to take advantage of their
included `go-sockaddr` library for getting the IP addresses we need in
a portable way. This particularly avoids problems with "predictable"
interface names provided by systemd.
Also adds the `sockaddr` binary to the Packer build so we can use it
in our provisioning scripts.
Make a clear split between Packer and Terraform provisioning steps:
the scripts in the `packer/linux` directory are run when we build the
AMI whereas the stuff in shared are run at Terraform provisioning time.
Merging all runtime provisioning scripts into a single script for each
of server/client solves the following:
* Userdata scripts can't take arguments, they can only be templated
and that means we have to do TF escaping in bash/powershell scripts.
* TF provisioning scripts race with userdata scripts.
