Dismiss immersive mode confirmation on setting changed to confirm

So the test won't be disturbed if the confirmation window was shown
before running the test.

Also change the strange invocation updateRotation to request
traversal of window hierarchy.

Bug: 185112691
Test: atest CtsWindowManagerDeviceTestCases
Change-Id: I2d18b5a14655418992f019c5a81c59a61db7ef3d