fdo#78159: fix import of OOoXML embedded objects

MimeConfigurationHelper::GetDefaultFilterFromServiceName() checks that
there is both an import and an export filter, and for OOoXML the export
has been removed; tweak the check to require only import for OOoXML.

Currently it still works invoke the OOoXML filter, but it is clearly
better to store the embedded documents only in ODF, so tweak
OCommonEmbeddedObject::store* methods to do that.

(regression from aeeaccf59abbc485d7786486f1accc1cb4d4dbf7)

Change-Id: Ib71f23fd110cbd4b570517f2dde2c53e3aa6301d
(cherry picked from commit 0b3d0fb2d9256dc6bae6af69ed494487004def75)
Reviewed-on: https://gerrit.libreoffice.org/9365
Tested-by: David Tardon <dtardon@redhat.com>
Reviewed-by: David Tardon <dtardon@redhat.com>