Fix ConfigurationDispatcherTest failure

The tests fail because RoundedCornerTest updated Confguration.EMPTY
value. This CL changes Configuration.EMPTY to new Configuration().

This CL also updates Configuration#toString to reflect the differences
of ScreenLayout round and compact_enabled, which was missed previously.

Test: run v2/android-virtual-infra/test_mapping/presubmit-avd via abtd
Flag: EXEMPT bugfix
Fixes: 400675837

Change-Id: Ia9975b93ef83a88e1dbced065f3ec814dad63460