fix [run.junit] -> [test.junit]

Testing Done:
https://travis-ci.org/jinfeng/jinfeng-pants-fork/builds/39534255

Reviewed at https://rbcommons.com/s/twitter/r/1256/
Sync of https://github.com/pantsbuild/pants/commit/3402620ffb49235de9f771ba126468d7bd25d7c1