Resolves: tdf#121887 RowModel::mnRow is 1-based, always

Basically this was always wrong.

Original code didn't treat the r attribute as optional and
resulted in an invalid -1 row for such cases, hence the RowModel
wasn't applied later.

Then

commit af8e6f4f544ecd01d3eda5f38bbd4779d5e8b2c6
CommitDate: Wed May 29 22:05:02 2013 +0200

    r is an optional attribute in c and r, fdo#65059

introduced a 0-based SheetDataContext::mnRow but assigned that to
a 1-based RowModel::mnRow as well if r attribute was missing, and
did not update SheetDataContext::mnRow if r attribute was given.

commit ff56553e34dfed01b9226ce7a516dbeb6da32124
CommitDate: Thu Mar 13 18:39:22 2014 -0400

    fdo#76032: This row index is 1-based whereas our own mnRow is 0-based.

then correctly assigned the decremented r attribute to
SheetDataContext::mnRow but did not touch the assignment to
RowModel::mnRow if r was not given. Probably confused by the
++mnRow already there which is correct but not sufficient for the
assignment.

Which we now finally fix herewith..

Change-Id: Iae1563ed01b95e7852ddad4fd59374c07186b493
Reviewed-on: https://gerrit.libreoffice.org/64580
Tested-by: Jenkins
Reviewed-by: Eike Rathke <erack@redhat.com>
(cherry picked from commit 76fbe494785faee1313d1c0be8ed2ca7b0d74f68)
Reviewed-on: https://gerrit.libreoffice.org/64639
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
diff --git a/sc/source/filter/oox/sheetdatacontext.cxx b/sc/source/filter/oox/sheetdatacontext.cxx
index 5f17d8c..9732ce6 100644
--- a/sc/source/filter/oox/sheetdatacontext.cxx
+++ b/sc/source/filter/oox/sheetdatacontext.cxx
@@ -272,7 +272,7 @@ void SheetDataContext::importRow( const AttributeList& rAttribs )
        mnRow = nRow-1; // to 0-based row index.
    }
    else
        aModel.mnRow = ++mnRow;
        aModel.mnRow = (++mnRow + 1);   // increment 0-based row index, to 1-based model row
    mrAddressConv.checkRow( mnRow, true);
    mnCol = -1;