Upgrade to Groovy 2.3.6.

Closes #399.
Shut down the created launch configs.
Print when tests start when building on a cloud CI server.
Test does not need to extend super class.
Shut down the launch configs.
Shut down exec controller.
Remove empty test class.
Bump thread count to avoid occasional dead lock.

This is a temporary fix.
No more travis.
Don't serialize tests for CI.
Parallelize the core tests.