Fix request #6290: invert order in follow ups comments is not saved as preferences

Use 'tracker' as it's the standard way to route toward a tracker.
So we leverage on Tracker_URL to check that users are allowed to see the tracker
they want to put preferences on.

Change-Id: Ic87c7572bf5c3648183a7caa7e5ed34f1043eb69
Merge commit 'refs/changes/22/2022/2' of ssh://gerrit.tuleap.net:29418/tuleap into tuleap-stable-master

* ssh://gerrit.tuleap.net:29418/tuleap:
  Fix request #6290: invert order in follow ups comments is not saved as preferences

Change-Id: I7b177318e1df458df9abfd6cc29ab5c0495f22d9
Tuleap 6.11.99.6

Change-Id: Ia926102bca280c5103bc5f89b869d8e11e82d4a8