migrated correctMysqlUsers() function to new PDO database class, refs #1287

Signed-off-by: Michael Kaufmann (d00p) <d00p@froxlor.org>
corrected Database::needSqlData() and Database::getSqlData(), refs #1287

Signed-off-by: Michael Kaufmann (d00p) <d00p@froxlor.org>