Save autostyle in the correct file.

When KoShapeSavingContext::AutoStyleInStyleXml is set styles auto styles needed to be written
to the styles.xml. This fixes the problem that the style in bug 296664 for the list was saved to content.xml
instead styles.xml.

BUG: 296664

Please review so I can backport to 2.4 branch.

Roundtrip tested with my odp and odt test set.

CCMAIL: calligra-devel@kde.org