Revert "test: Remove complicated JSON->shell dict logic"

This reverts commit 60b4d237fb9f56ee86c14147af3db61209f99717.

Using a bash associative array provides a significant performance
improvement (~40s / 43% reduction). Re-add that functionality but use jq
to do the processing instead of python.

Change-Id: Ib49cf69676c3187ceb1e26ac1ca3686609484036