IL-709 Fix issues with Terraform state locking and stale processes

[thomashashi]

See https://support.instruqt.com/support/tickets/137 --- we can no longer rely on Instruqt to stop all shell tab processes as you move from one challenge to another, which causes two problems with this track: 1) users sometimes check whilst a Terraform command is still running, which causes subsequent confusion when they run terraform again and get error messages about the state being locked; 2) We tell users to start blast-radius, which may be running when we tell them later on to start it again, and they get port already in use errors.

• Where we run terraform commands in a challenge, update the check script to ensure that Terraform is not still running
• Fix a bash error which was causing a check for google_compute_subnetwork to fail because we did not quote what could be an empty string
• Make some checks a little more robust
• In the tf-graph challenge
  • Make the check for it running more robust
  • And then if it is running, shut it down so we do not get errors later on
• Clarify instructions in the add-virtual-network challenge

[thomashashi]

Please wait until I get some folks to test

[thomashashi]

Test track is FYI https://play.instruqt.com/hashicorp/tracks/zzz-il-709-terraform-intro-gcp/