--replay-tracking is enabled, we can't set
1, because we don't want to force the request to be recorded (according to: http://piwik.org/docs/tracking-api/#toc-two-tracking-methods-image-tracking-or-using-the-api).
I just tested to add a piwik.php request with &rec=0 and the line is not tracked. So is this change really fixing a bug? if so, what bug?
rec=0 should not be recorded.
The bug was that when we had piwik.php?idsite=1 (default img tag, without rec=1), it was recording the visit (but it shouldn't).