Providing a different URI to be used for logging

#### What's this PR do?
Allows a different database URI to be used for logging. This variable is now setup on the production environment and with this deploy, it should fix winston logging to the MongoDB.

#### Any background context?
A little more info on the bug itself - our DB URI defines a replica set. `winston-mongodb` requires the name of the replica set to be included in the URI. Our original `DB_URI` doesn't include it. It is included though in the `LOGGING_DB_URI`.