Don't scroll to home card if overview isn't visible

Consider these steps:
- Swipe up for recents
- Scroll over several cards
- Swipe up for all apps
- Press home

Before this change, there was a delay as recents scrolled back to
the workspace card before going home, even though it wasn't visible.

Change-Id: I1c0edc8e02d1d1d236f47882695903e33e6b09ae