SystemUI: Fix missing top task in recent panel.

If preloadRecentTasksList was not called or was called too
late and RecentsActivty already started and last top activity has
excludeFromRecents flag setted it might be missing
from recent application list.

Change-Id: Idf7153824805ceea9fcaf04ac645b73a5e93a4d9
Merge "SystemUI: Fix missing top task in recent panel." into kitkat