kiji-scoring: SCORE-191. Improve reliability of TestInternalFreshKijiTableReader#testStatistics

issue: https://jira.kiji.org/browse/SCORE-191
review: https://review.kiji.org/r/2171
commit: https://github.com/kijiproject/kiji-scoring/commit/b1d4dabe9827ed96abe19dfd86b6b60569e898f9