BUG: fix fields instanciation, must be done once
BUG: fix fields instanciation, must be done once

     This bug occurs when testing kml writing using OGR
     Fixing this bug, allow us to use OGR for KML writing
     Note: Fields are not reported when writing neither with OGR nor
     with KMLVectorDataIO

orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB