Bug 10731: fix use of IntranetSlipPrinterJS by hold slips

Bug 10731: fix use of IntranetSlipPrinterJS by hold slips

Hold slips aren't printing automatically with JS Print Setup because it
appears the system preference IntranetSlipPrint is never being passed to
the template.

Test Plan:
1) Set up JSPrintSetup
   http://wiki.koha-community.org/wiki/Setting_up_slip_printer_to_print_silently
2) Place a hold
3) Check the item in to capture the hold
4) Click "Print and confirm"
5) Note the slip does not print automatically
6) Apply this patch
7) Repeat steps 2 through 4
8) Observe that the slip now prints automatically

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>