If no fill type is defined for a table cell, then set it to XML_noFill
explicitly, in order to override the fill type defined by the default
graphic style or the graphic style named standard, added by LO and
exported into ODP.

Change-Id: I9c5aa4c2a939ee7b8c75ae686d845cd14a718254
Reviewed-on: https://gerrit.libreoffice.org/22618Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>
Tested-by: Katarina Behrens <Katarina.Behrens@cib.de>