Fix critical bug: t3lib_DB::sql_error always returned last error from DB-Master (even if DB-SLAVE was used to execute SQL-SELECT-statement)

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/t3p_scalable/trunk@81619 735d13b6-9817-0410-8766-e36946ffe9aa