LUCENE-4396: add test case

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1617284 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6304 JsonLoader should be able to flatten an input JSON to multiple docs

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1617287 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6362: fix test bug

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1617289 13f79535-47bb-0310-9956-ffa450edef68