If home activity is not fullscreen keep drilling.

When the home activity launches a non-fullscreen activity as part of
its own task then ensureActivitiesVisibleLocked() must continue past
the launched activity when determining activities to show and hide.
Stopping at the non-fullscreen activity leaves the fullscreen home
activity hidden.

Fixes bug 11555762.

Change-Id: I9058d8cde3a41cb7f9b1f97e5c0cb32e9b0f5af7