PTS should be disabled when running experiments

[erichaagdev]

When PTS is enabled, test tasks/goals will only store their results in the build cache if build caching is enabled, all tests are selected for execution, and the task/goal was successful. This can throw off the experiment results when PTS decides to skip tests. For this reason we should disable PTS when running the build caching experiments as the focus is on optimizing build caching only.

We can use the system property pts.enabled to disable PTS.