Add test for multi-package rollback.

The test is marked @Ignore for now because we don't yet properly support
rollback of multi-package installs.

Test: atest RollbackTest (with selinux disabled).
Test: atest RollbackTest fails without the @Ignore.
Bug: 112431924

Change-Id: Ia76d48756bc1078344dcf1f2c5696ab79eb0c40c