Try to fix IME multi-display tests flaky

There's a chance that IMS moves from the default display to the first
simulated display and receives #onConfigurationChanged callback,
which makes the test flaky.

This CL changes to verify #onConfigurationChanged callback when top
focused display is movd to the first display to reduce flakiness.

Test: forrest run testNoConfigurationChangedWhenSwitchBetweenTwoIdenticalDisplays * 100
Bug: 195903192
Change-Id: Id6d8abf15ca5d522316b920aa70d421871f55186
1 file changed