Dream when user activity times out while docked if appropriate.

If the user has requested that dreams start when docked and a user
activity timeout occurs, then start dreaming assuming all of the
other usual conditions are appropriate for dreaming (the device is
powered, etc.).

Previously dreams only started when the device was initial docked
but not if the device fell asleep while remaining docked.

Bug: 7281240
Change-Id: I72c3f854fd1ae8e6615f4fa6e4c4ecd8de37c84b