Recompute focus in showLw if needed

When the status bar window was relayouted it wasn't visible by
policy (yet). Thus, it couldn't get focus even though
FLAG_NOT_FOCUSABLE was not set. Shortly after, it was made
visible and thus able to receive focus, but nobody actually
kicked off another focus calculation.

Test: Set device password, open camera from lockscreen,
adb shell wm dismiss-keyguard
Fixes: 36242569

Change-Id: Iafbeac45d25490243b701434008e65f545cebbdf