TIF: Remove the uniqueness check for track ID from notifyTracksChanged

Requiring uniqueness of ID across all track types seems a little too
much demand for developers and they do want to use the same ID on
different track types. Also, this doesn't seem terribly useful.
Hence remove the check.

Bug: 28436618
Change-Id: I9040310c5ce31bcff522021d83f7508506cbd9d3