LUCENE-5611: always abort if we hit exc in StoredFieldsWriter.start/FinishDocument

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1591657 13f79535-47bb-0310-9956-ffa450edef68
fix test bug / add toStrings

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1591658 13f79535-47bb-0310-9956-ffa450edef68