kiji-mapreduce: KIJIMR-261. Broken progress reporting in KijiTableInputFormat

 - Fix typo when computing mStopPos (using InputSplit.getStartRow instead of getEndRow).
 - Add proper unit-tests.
 - Discard disabled hadoop2-specific test.

issue: https://jira.kiji.org/browse/KIJIMR-261
review: https://review.kiji.org/r/1530
commit: https://github.com/kijiproject/kiji-mapreduce/commit/7a007f97f3a6fa4d30cec07bf7d362432e878529