Only return to home if the foreground task is removed.

The previous fix that returned to home when a task on top of home was
removed was too broad. If that task was not the foreground task it was
not a good idea to bring the home screen to the front.

Fixes bug 11198552.

Change-Id: I14e5fdc167011f25e0e8490c3e52c5c1dcbffbff