Move last of tests to tests directory

The following commit: a016838546f695cbecdd69b2742d36d7c8dbadc6
moved all the tests here but the plexxi one slipped in before it
was merged and the policy/builtins/tests was left out by mistake.
This patch corrects this.

Change-Id: I36d7654396102b277ad900a158afafa216a022fb