Update PB get index call

Updated to use newer index results record like the other 2i tests. It
was failing before this as it was using the old tuple result format.

http://giddyup.basho.com/#/projects/riak_ee/scorecards/43/43-571-verify_secondary_index_reformat-ubuntu-1004-64-eleveldb/18223/artifacts/163436

/cc @rzezeski