Bug 18707: Background jobs post disabled inputs

Bug 18707: Background jobs post disabled inputs

For example, in Tools > Batch item modification input of deleted subfields are disabled.
This form is posted using background job via JS code.
Looks like this JS code converts a POST form into a GET URL, including inputs that are disabled :

koha-tmpl/intranet-tmpl/prog/js/background-job-progressbar.js
function submitBackgroundJob(f) {
...
$(':input', f).each(function() {
...

This patch add a :enabled to selector

Test plan :
<to define>

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>