kiji-scoring-server: SCORSRVR-6. ScoringServer should check if there is a load balancer base url in the system table

issue: https://jira.kiji.org/browse/SCORSRVR-6
review: https://review.kiji.org/r/1660
commit: https://github.com/kijiproject/kiji-scoring-server/commit/77fa3e2811da83bd467508553e7caa968ed38150