Fix the following error:

> File "autonetkit/ank_messaging.py", line 107, in publish_data
>     log.info("Unable to connect to HTTP Server %s: e" % (http_url, e))
> TypeError: not all arguments converted during string formatting

When trying to generate cfg's without having the visualisation server running
Merge pull request #124 from oliviertilmans/http_vis

Fix a small log.info error