related tdf#117816, the dxf ID is a global and not a sheet property

Change-Id: I4c5ca66ce550de74d8b9396aa0213c558b7f884f
Reviewed-on: https://gerrit.libreoffice.org/57445
Tested-by: Jenkins
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
(cherry picked from commit 0f0466c6)
Reviewed-on: https://gerrit.libreoffice.org/72008Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>

sc/qa/unit/data/contentCSV/new_cond_format_test_sheet2.csv

 2.00,2
-1,1.00
+1,1.000
 4.00,3

sc/source/filter/excel/xestyle.cxx

@@ -2983,12 +2983,12 @@ XclExpDxfs::XclExpDxfs( const XclExpRoot& rRoot )
     mxFormatter->FillKeywordTableForExcel( *mpKeywordTable );
 
     SCTAB nTables = rRoot.GetDoc().GetTableCount();
+    sal_Int32 nIndex = 0;
     for(SCTAB nTab = 0; nTab < nTables; ++nTab)
     {
         ScConditionalFormatList* pList = rRoot.GetDoc().GetCondFormList(nTab);
         if (pList)
         {
-            sal_Int32 nIndex = 0;
             for (ScConditionalFormatList::const_iterator itr = pList->begin();
                     itr != pList->end(); ++itr)
             {