kiji-schema: SCHEMA-857. Fix Cassandra after breaking change in SCHEMA-851

issue: https://jira.kiji.org/browse/SCHEMA-857
review: https://review.kiji.org/r/1995
commit: https://github.com/kijiproject/kiji-schema/commit/a56fbb332508d2cc6f84b6a5984dfbd8bc300aa3