Do not remove the default display during tests.

The default display is used by some tests that exercise features only
functional only on the default display (like policy rotation). This CL
makes this display not get removed with the created test displays and
ensures no collision in id space from a previous test run (done in the
test setup).

Change-Id: Ia14b9c023c779d263283fe8c7b512dca17ff312f
Fix: 36385757
Test: bit FrameworksServicesTests:com.android.server.wm.StackWindowControllerTests#testRemoveContainer_deferRemoval