While it is helpful to know exactly which commit in a many-commit PR caused test failures, there is only so much ocean to boil, and most of the time we care only about the final commit passing tests before merging.

Update our Drone configuration to abort any continuous integration tests being run against previous commits. This could be sliced up a bit, so the highest value would be in terminating Sauce Labs UI tests, and the least value being in terminating unit tests.