Fix IME related tests

The IME layer is sometimes present but hidden on the hierarchy. The tests should ignore this condition and ensure that the IME window is displayed only once.

Test: atest FlickerTests
Change-Id: I2b4602a6b517716dd032f89d213c2341f445237e

tests/FlickerTests/src/com/android/server/wm/flicker/OpenImeWindowTest.java

@@ -56,6 +56,7 @@ public class OpenImeWindowTest extends NonRotationTestBase {
     @Test
     public void checkVisibility_imeWindowBecomesVisible() {
         checkResults(result -> WmTraceSubject.assertThat(result)
+                .skipUntilFirstAssertion()
                 .hidesImeWindow(IME_WINDOW_TITLE)
                 .then()
                 .showsImeWindow(IME_WINDOW_TITLE)