Ensure screenshot layer appears during rotation

Add some additional checks on flicker tests to ensure that the screenshot layer ir correctly being displayed during the rotation animation.

Test: atest FlickerTests:ChangeAppRotationTest, atest FlickerTests:OpenAppColdTest and atest FlickerTests:OpenAppWarmTest
Change-Id: I2a6c74179c07eee86caae08f05430752aa4e084e