Bug 34689: Ignore itemnumber when creating item hash

A primary key error can be thrown when an item number is included in a new title hash. We need the item creation to ignore an itemnumber even if it is included in a MARC Framework

Test plan:
1) Edit the MARC framework relating to books (BKS in KTD)
2) In the 952$9 field (Koha itemnumber (autogenerated)), change the value of "Managed in tab" to "items (10)"
3) In the catalog, find a record that uses that MARC framework
4) Click "New" and choose to add a new item
5) Enter a barcode and click the "Add & duplicate" button
6) The page will refresh and an item will have been added
7) Enter a new barcode and click the same button again
8) An error will be thrown
9) Click the back button in the browser
10) Apply patch and restart_all
11) Click the add and duplicate button again
12) This time no error will be thrown and the page will refresh with another new item added
13) Sign off!

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit 5b9dbe558f)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>

cataloguing/additem.pl

@@ -262,6 +262,7 @@ if ($op eq "additem") {
             }
             $item->more_subfields_xml(undef);
         } else {
+            next if $c eq 'itemnumber';
             my @v = grep { $_ ne "" }
                 uniq $input->multi_param( "items." . $c );