ui: unconditional to-disk logging should be de-configurable

[ghost]

What version were you using?

git HEAD, concerns this file in the most recent revision to-date: https://github.com/LearningLocker/learninglocker/blob/901bc715d1051b5343fdd4e757300027f3ad0e3f/ui/src/server.js#L52

What steps can we follow to reproduce the behaviour?

Build the LearningLocker application and launch all services, for example with any of the provided pm2.json configs; disable logging to disk by making pm2 log stderr and stdout to /dev/null. Enable logging to CloudWatch using the Winston environment variables instead, or divert logs otherwise.

What is the actual behaviour?

Because of https://github.com/LearningLocker/learninglocker/blob/901bc715d1051b5343fdd4e757300027f3ad0e3f/ui/src/server.js#L52 , the UI process will continue logging to disk unconditionally, ignoring all logging-related settings.

What is the expected behavior?

The UI process should integrate well with the behaviour of the other modules: Log to stdout/stderr by default, integrate with Winston if configured, offer ways to disable file logs.

Is there any additional information that will help us replicate/understand the problem?

Uncontrolled logging to disk is not desirable for example in containerized runtime environments. The behaviour of just this submodule is unintuitive.