Change NGINX config check handler directory

[alessfg]

Proposed changes

Change the command directory when running the NGINX configuration check handler to prevent edge case errors when the handler is run from a directory that the NGINX process' user does not have access to.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• I have added Molecule tests that prove my fix is effective or that my feature works
• I have checked that all Molecule tests pass after adding my changes
• I have updated any relevant documentation (defaults/main/*.yml, README.md and CHANGELOG.md)