Cert provisioning script `generate-certs.sh` incorrectly copies the entire TLS "result" directory instead of the certs themselves.

This line is wrong:

https://github.com/ericwastaken/Docker-RabbitMQ/blob/7ce9bc942a7628dd41466f5667d45559051176c9/rabbitmq/provisioning/generate-certs.sh#L19

Should probably be the following, though it needs to be tested:
```shell
cp -r result/* ../../../config/certs/ 
``` 
