kiji-mapreduce-lib: KIJIMRLIB-29. Fix resource leak in integration test

issue: https://jira.kiji.org/browse/KIJIMRLIB-29
review: https://review.kiji.org/r/1858
commit: https://github.com/kijiproject/kiji-mapreduce-lib/commit/b5f3d7f6d9d7ffa184ddd01c2ccc96920a52ceec
kiji-end-to-end-tests: EXP-437. Fix regression in the the Express music end-to-end test.

issue: https://jira.kiji.org/browse/EXP-437
review: https://review.kiji.org/r/1848
commit: https://github.com/kijiproject/kiji-end-to-end-tests/commit/ad6ed3addbafd3490b99b22d2c9b7afe5bc66006