Remove hardcoded path to credentials file

[sharifelgamal]

Currently the path the creds file we look for is hardcoded to /var/lib/minikube/google_application_credentials.json which is not ideal. Let's remove that dependency.

[Baune8D]

This would be great. We use this project with Kind instead of Minikube, and having to mount credentials to that path is quite akward.