Cannot disable secure connection to minio storage backend

[xaniasd]

When downloading models (e.g., for MLFLOW_SERVER deployment), from a minio backend, a secure connection is enforced. While this is a sane default, it is a problem for local deployments where TLS is tricky to set up. MLFlow itself does not pose such a requirement.

This should either be configurable via an environment variable or detected automatically from the configured scheme for Minio