kiji-scoring: SCORE-169. Disable parallel test execution until a workaround is in place for localjobrunner threadsafety

issue: https://jira.kiji.org/browse/SCORE-169
review: https://review.kiji.org/r/1717
commit: https://github.com/kijiproject/kiji-scoring/commit/17d3bd34e95ff7dea68243fb8486c49e1a25652e