GeoServer: Returns broken SLD version 1.1.0 for styles published as 1.0.0

[index-git]

Steps to reproduce:

• publish sample/style/basic.sld (1.0.0)
• ask for the style with headers of SLD 1.1.0
• GeoServer returns

<?xml version="1.0" encoding="UTF-8"?>
<sld:StyledLayerDescriptor xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:se="http://www.opengis.net/se"
                           xmlns:gml="http://www.opengis.net/gml" xmlns:ogc="http://www.opengis.net/ogc"
                           xmlns:sld="http://www.opengis.net/sld">org.geotools.styling.StyledLayerDescriptorImpl@544d668e
</sld:StyledLayerDescriptor>