wire these integration tests to the tests/python/pants_test:integration target

"All integration tests should be wired up to the tests/python/pants_test:integration target, I think."

oh yeah, good idea; that's probably what it's there for, d'oh

Testing Done:
./pants tests/python/pants_test/BUILD:integration

Now runs fou^W FIVE tests.

Reviewed at https://rbcommons.com/s/twitter/r/543/