always provide class loader when creating JAXBContext

Change-Id: I27d6e079cf3e148f8468b1ca8e8adb771ece837e
Reviewed-on: http://gerrit.esdi-community.eu/3138
Reviewed-by: Simon Templer <simon.templer@igd.fraunhofer.de>
Tested-by: Jenkins <sitemple@igd.fraunhofer.de>