Disable Terraform integration tests for forks

[strickvl]

TF Secrets are used so we disable integration tests on forked copies of the repository (i.e. community contributions).

Pre-requisites

Please ensure you have done the following:

• I have read the CONTRIBUTING.md document.
• If my change requires a change to docs, I have updated the documentation
  accordingly.
• I have added tests to cover my changes.
• I have based my new branch on develop and the open PR is targeting
  develop. If your branch wasn't based on develop read
  Contribution guide on rebasing branch to develop.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to
  change)
• Other (add details above)