fix logger issue

[paul90]

defining morgan token is problematic. It wrongly reports requests are all to the last wiki server started.

[WardCunningham]

What is a morgan token?
See https://expressjs.com/en/resources/middleware/morgan.html

[WardCunningham]

The Morgan API doc says:

The format function will be called with three arguments tokens, req, and res, where tokens is an object with all defined tokens, req is the HTTP request and res is the HTTP response. The function is expected to return a string that will be the log line, or undefined / null to skip logging.

This must be part of the Express middleware that I don't fully understand. I'd like to know more but don't let my ignorance hold up this useful correction.