redis error message when port already in use

[clewis7]

Issue when installing and running the minimal example off of the dev branch. I had just installed redis, and the server was already running on the default port. Therefore, when I tried to run the demo, it produced the following error message:

Unable to read server start time from global.log.
This may be because the server could not be started or did not log its activity.

Simply calling:

sudo systemctl stop redis-server

before launching the demo fixed the issue.

I think we should add another line to this error message or state somewhere in the documentation that users should try this fix for this particular error. @jmxpearson I'm happy to make a PR to add something in the docs or the error message, just let me know :D