download terraform.py using local_exec

[langston-barrett]

• Installs cleanly on a fresh build of most recent master branch
• Upgrades cleanly from the most recent release
• Updates documentation relevant to the changes

fixes #1120

[sehqlr]

Is there anything else we need to do for this, or just testing?

[langston-barrett]

@sehqlr You tell me! This has passed it's CI builds, so I'm not sure it even needs testing, just merging.

[sehqlr]

@ryane: What do you think? Can we include this in 1.3?

[ryane]

I'm just wondering if we need a little documentation around upgrades. For example, it looks a user would have to run terraform apply or the equivalent curl command to download the inventory script.

And, when we bring this in, we'll definitely want to make sure the updated sample tf files are mentioned in the release notes (#1733)

[thomasvincent]

thanks!

[Theaxiom]

Let's get the base branch stabilized before approaching this.

comment, not review

[thomasvincent]

Resolved conflicts