Don't queue unnecessary discontinuity when switching tracks

NuPlayer originally would block on track switch until it receives a
discontinuity from each track (audio/video). This limitation has been
addressed in commit 53904f372b9c4a5ea7f839012b52b3d564e41207.

Bug: 23740080
Change-Id: I348f825ffba227904127b86c968b0acac9fd70d4
1 file changed