OAK-1987 - LuceneIndex should access Lucene Directory if query involves FullTextSearch for cost calculation

Change the order of check. Index would now only be accessed only when query has a full text constraint

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1613018 13f79535-47bb-0310-9956-ffa450edef68