Set a shorter timeout for logging a warn on slow IUserSwitchObservers.

On automotive, it helps identify slow services. For example:

W ActivityManager: User switch delayed: observer #1
  WallpaperManagerService sent result after 1608 ms

Without this change, the WallpaperManagerService wouldn't be logged
because the "give up" timeout is 3000ms.

Bug: 145558164
Bug: 144801993

Test: manual verification (see logcat above)

Change-Id: I68e3b7220bbac25075e4fd4dad83c3a26b88940c