Don't finish noHistory="true" activities behind the lock screen

The foreground activity is stopped when the device goes to sleep,
and started again when the device is unlocked.  We now distinguish
this case from a "normal" stop, and do not finish() a foreground
noHistory="true" activity inappropriately when the device sleeps.
We also detect the case where an activity is started while the
device is still asleep, in which case the foreground noHistory
activity is cleaned up as part of bringing the new activity to
the foreground.

Bug 6657549

Change-Id: I9c6a0830aed0e47e4207b62803b90067c8486112