Tests sometimes ask for nextPosition() after calling docs()

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene2878@1643587 13f79535-47bb-0310-9956-ffa450edef68
Fix some more places that were returning -1 from nextPosition()

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene2878@1643589 13f79535-47bb-0310-9956-ffa450edef68