Check for field names in SimpleField rather than SimpleData
Check for field names in SimpleField rather than SimpleData

Doing so makes the test also succeed with gdal-1.10
See http://trac.osgeo.org/gdal/ticket/5208

calvinmetcalf/CartoDB-SQL-API,calvinmetcalf/CartoDB-SQL-API,dbirchak/CartoDB-SQL-API,dbirchak/CartoDB-SQL-API,CartoDB/CartoDB-SQL-API,calvinmetcalf/CartoDB-SQL-API,dbirchak/CartoDB-SQL-API,dbirchak/CartoDB-SQL-API,CartoDB/CartoDB-SQL-API,calvinmetcalf/CartoDB-SQL-API