Resolve #805

Prior to this change, if the Medusa process exits with a non-zero exit code for some reason, the Medusa container will be stuck forever because of the while true loop.

With this fix, the while loop will be interrupted if the Medusa process exits, and the container will exit with the same code as the Medusa process exit code.

To validate this change, I've manually tested the following scenarios:

• Start the medusa container without any file at /etc/medusa.ini -> the container should exit with a non-zero code.
• Start the medusa container with a valid config at /etc/medusa.ini -> the container should run as expected.
• Change the config /etc/medusa.ini while the container is running -> the container should exit with a zero code.
• Put an arbitrary sys.exit(42) in server.py to mock a production issue -> the container should exit with the status code 42.