Only add tracking categories to "real" file pages

The file namespace also contains:
* File redirect
* Random pages that have no business being there
* Local pages with additional details from foreign files
None of which should be in the tracking category.

Change-Id: I9a6f4fa5bccc1a4ff875103b1ad95dae65f23074
Follow-up: bef043790e23c04b6
(cherry picked from commit 8f00e8fae8a0745637ffc0a43885824cb18f39a9)