fix: Change terraform_validate hook functionality for subdirectories with terraform files (#100)

* Update terraform_validate.sh:
-Change to the directory before running terraform validate to use the Terraform
 configuration for the appropriate working directory.

* Neglected to change the terraform validate call to use the default of the
current directory.

* Several changes to improve functionality:
- Switch to checking the path for '*.tf' instead of always checking the current
  directory.
- Try to find a '.terraform' directory (which indicates a `terraform init`) and
  change to that directory before running `terraform validate`.

* Fix the description for the terraform_validate hook to reflect changes that were
made in:
35e0356188

* - Clean up comments.
- Adjust variable names to better reflect what they are holding.

.pre-commit-hooks.yaml

@@ -35,7 +35,7 @@
   exclude: \.terraform\/.*$
 
 - id: terraform_validate
-  name: Terraform validate without variables
+  name: Terraform validate
   description: Validates all Terraform configuration files.
   entry: terraform_validate.sh
   language: script