Ignore wallpaper relaunch timeout during shutdown

Because of course during system shutdown, the wallpaper service
won't actually get relaunched.  Sometimes shutdown can take long
enough that this timeout kicks, so we need to avoid clearing the
live wallpaper state spuriously.

For simplicity we just check at "would have timed out now" time
rather than try to distinguish between the shutdown case and a
genuine crash that raced with the shutdown broadcast.

Bug 32020355

Change-Id: I9335b2c0214b4c750ef950fed157d186aa670176