Preventing from re-create starting window.

Unlock device will also request to create starting window for visible
activities, if core just remove first starting window after app window
drawn, there can have a slightly timing gap to request another starting
window.
It should be much stable by modify the check condition to window type,
instead of finding local member.

Bug: 322547402
Test: after start activity on lockscreen, unlock immediately to simulate
the second create starting window request.

Change-Id: Icbc07fcf3f2c7a5fae2fc13f28f519885ae5054a