Noisy requests to root endpoint in trace log

[ben-sagar]

This line:

https://github.com/DEFRA/ivory/blob/develop/server/services/cookie.service.js#L9

Is writing out a message to the console four times every minute, at 15, 18, 45 and 48 seconds:

Session cookie not found for page /

This causes a lot of noise in the App Insights trace, making it difficult to diagnose problems.

It is also generally unhelpful to have the root endpoint being repeatedly pinged like this as this also shows as noisy GET requests in the App Insights log.

[ben-sagar]

The root endpoint home.route.js is correctly sending through a value of false for the displayLogMessage parameter, but for some reason the cookie service does not refer to that parameter and just logs the message anyway.

A simple fix is to actually implement the check for which the displayLogMessage parameter was presumably originally intended.