use FSDirectory to avoid OOME

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1594182 13f79535-47bb-0310-9956-ffa450edef68
er, wrong test

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1594184 13f79535-47bb-0310-9956-ffa450edef68