Fix ReOpenImeWindowTest flicker test for shell transitions

In this case, legacy transitions is incorrect because it was
written before live-tiles and, due to some quirk, still manages
to pass the now-incorrect test. However, the test is technically
wrong and thus shell transitions doesn't pass. This CL fixes the
tests when shell transitions is enabled.

Specifically, there are a few tests explicitly called "X is ALWAYS
visible" which should test that the window in question remains
visible throughout the test. However, the test was adjusted to
test that the windows go away and come back. With shell transitions
the windows behave correctly, so we can remove the adjustments.

Bug: 193565597
Test: atest ReOpenImeWindowTest
Change-Id: I33c5b6327e5b5762958b66ff20d5fe67b9566c10