OSGI-INF/service-component/null.xml is removed now after creation, but
unfortunatly, target folder is also removed in phase prepare-package
with use of clean-plugin version 2.6.1 or 2.3 and use of property
excludeDefaultDirectories target folder is not deleted any more, but
unfortunatly, the file null.xml is not deleted too :-(
null.xml is now removed, currently it is unclear, which of the two
filesets caueses the deletion. Next step will be to move the clean
plugin specification to parent-modules in pepper project