fix: use -chdir and -upgrade in terraform_validate wrapper

- This tool doesn't clean up any generated lockfiles; if a lockfile
  already exists (from a previous run), it's possible to get an error
  like
  "locked provider registry.terraform.io/hashicorp/google 6.4.0 does not
  match"
- Use Terraform's `-chdir` option rather than `cd`

Author: wyardley

infra/build/developer-tools/build/scripts/task_wrapper_scripts/terraform_validate

@@ -19,8 +19,5 @@
 # files to validate.  This directory is assumed to be a root module.
 
 set -eu
-curdir=$(pwd)
-cd "${1}"
-flock -x /workspace/.terraform.lock -c "terraform init -backend=false >/dev/null"
-flock -s /workspace/.terraform.lock -c "terraform validate"
-cd "$curdir"
+flock -x /workspace/.terraform.lock -c "terraform init -upgrade -chdir=$1 -backend=false >/dev/null"
+flock -s /workspace/.terraform.lock -c "terraform -chdir=$1  validate"