Fix issue #37938835: Undismissable "Camera is running in the...

...background" notification even after force stopping camera

Ensure we have a message scheduled to dismiss the next app every
time we go through the app list.  Also don't show the notification
for an app when it is in the foreground.

Test: manual

Change-Id: Idd93c8d9f8252b880c8b4bf069c71ad71a6b27c9