SOLR-5652: in cursor tests, don't sort on 'plain' docvalue fields (i.e., those using standard Lucene sorting for missing values) when the codec doesn't support missing docvalues.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1566741 13f79535-47bb-0310-9956-ffa450edef68