Temporarily enable CI to test against enterprise instance

[sebasslash]

Description

We are temporarily enabling CI to test against an enterprise-configured instance (TFE). These do not suffer from the same concurrency issues as our cloud-configured test instances. What this means for the time being is that cloud-only tests must be run manually and the results added to the PR description/comment.

Remember to:

• Update the Change Log
• Update the Documentation

Testing plan

1. Describe how to replicate
2. the conditions
3. under which your code performs its purpose,
4. including example Terraform configs where necessary.

External links

Include any links here that might be helpful for people reviewing your PR. If there are none, feel free to delete this section.

• go-tfe documentation
• API documentation
• Related PR

Output from acceptance tests

Please run applicable acceptance tests locally and include the output here. See testing.md to learn how to run acceptance tests.

If you are an external contributor, your contribution(s) will first be reviewed before running them against the project's CI pipeline.

$ TESTARGS="-run TestAccTFEWorkspace" make testacc

...