ACCUMULO-1361 committing Corey Nolet's for zero-length ColumnVisibility

git-svn-id: https://svn.apache.org/repos/asf/accumulo/branches/1.5@1477732 13f79535-47bb-0310-9956-ffa450edef68
ACCUMULO-1361 committing Corey Nolet's patch for zero-length ColumnVisibility

git-svn-id: https://svn.apache.org/repos/asf/accumulo/trunk@1477733 13f79535-47bb-0310-9956-ffa450edef68