[Qual] Use jQuery property instead of attribute to test and set disabled

htdocs/admin/mails.php

htdocs/admin/menus/edit.php

htdocs/barcode/printsheet.php

htdocs/comm/action/card.php

htdocs/core/class/html.formactions.class.php

htdocs/core/lib/ajax.lib.php

htdocs/core/tpl/admin_extrafields_add.tpl.php

htdocs/core/tpl/admin_extrafields_edit.tpl.php

htdocs/install/fileconf.php

htdocs/product/stock/tpl/stockcorrection.tpl.php

htdocs/user/card.php