Fix minimized dock stack for translucent activity over home task

Previously, we only looked at whether home task is going away or
getting visible. This doesn't work anymore, as we also need to
un-minimize docked stack if another task is visible with translucency
over the home task.

Change-Id: I993f58a25d99d2ef9f562f7d1587c2dec0d05142
Fixes: 28434466
Fixes: 27906038