Ensure that the gesture animation video is paused properly.

Add the handling to pause the animation video when user navigates away
from the gesture settings.

Test: Manual - play gesture animation videos, then switch to another app
in recents. Verifies from logcat that NuPlayerDriver is not active.
Fix: 32064123

Change-Id: I3d0fb3946e4d0d77a686aa97cfabe667862cac17