if bAutoStyles is true then the mbDoSomething of the SvXMLElementExport is
false, and the ctor/dtor doesn't do anything so any attributes added to the
exporter are not cleared by the SvXMLElementExport dtor

so only add the attribute if bAutoStyles if false and might as well extend the
block to cover the use of SvXMLElementExport and use the other ctor which
defaults mbDoSomething on

Change-Id: If35cd35e902372562fd7e78b3f970d91fcec3c16