Supply a plugin-dir argument to the terraform initialization scripts

[glennmusa]

Benefit/Result/Outcome
To deploy MLZ when disconnected from the internet.

Description
Today, due to same change beyond our knowledge, configuring Terraform to use the local Terraform provider cache will still pull the providers, however, Terraform CLI will still attempt to query for the provider metadata from the internet.

We'd like to provide a way to deploy completely disconnected from the internet. Setting the -plugin-dir=${TF_PLUGIN_CACHE_DIR} argument on any terraform init operations seems to solve this problem today.

There could be other ways to remediate this problem through .terraformrc or other configuration means, but for today, setting this argument seems to solve the problem.

Per our Dockerimage:

ENV TF_PLUGIN_CACHE_DIR=/usr/lib/tf-plugins

Acceptance Criteria

• Set the TF_PLUGIN_CACHE_DIR when doing terraform init in apply, destroy, and initialization functions