[bug] unable to set up ssl connection to AWS rds

[shawnazhaoxy]

I was trying to use the docker image to set up ssl connection to rds, I hit into some issues:

1. I realised in run_goose.py there are environment variables set up for setting up ssl. However, the environment variable is not set in docker-compose file.
2. with the environment variable MF_METADATA_DB_SSL_ROOT_CERT in run_goose.py, we need to parse in the local file path of the certificate, would it be possible to set up a folder in this repo to store some common ca certificates for database so that we can parse in the certificates easier?