MM: restore the non-saving wizard behaviour

The wizard didn't save the MM source document, even if it was modified.

Change-Id: I0c7fb6abd31934bab7a33d7a9c93222af3e35ee5
Reviewed-on: https://gerrit.libreoffice.org/10986
Reviewed-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>
Tested-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>