Finish handwriting session for recents gesture

Finish stylus handwriting session when user swipes to recent.
Bug: 223748964
Test: Manually:
     1. Open an app with editor
     2. swipe on editor with stylus [or emulated stylus]
     3. Observe ink trail drawn on screen
     4. quickly sipe to recents, ink should go away.
     5. repeat steps 1-3 for swipe to home

Change-Id: Id750ff55cb447247c3eca75daf37cb5aeb1d0cfa