OOXML embedded objects are converted to ODF during export, which
prevents the export from working, as it expects a stream, and ODF
uses a storage.

There is already a unit test in testEmbeddedXlsx, but it wrongly
succeeds because the components necessary to convert from OOXML to ODF
are missing in the test environment.

(cherry picked from commit 1dac99e7)
(cherry picked from commit 290cac71)

sw: un-break DOCX formula export

(regression from 1dac99e7)

(cherry picked from commit 3b63d2b9)

Change-Id: Ib4df346e04ecfb54ec1a728535be876db921b884
Reviewed-on: https://gerrit.libreoffice.org/20469Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
(cherry picked from commit 7689b7b7)