xmlloader: trivial cleanups in XMLLoader

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
xmlloader: fix for UriAccessor on Windows

See https://github.com/killbill/killbill/issues/226.

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
concurrent: fix tests failures on Windows

See details in https://github.com/killbill/killbill/issues/226.

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>