Bug 19388: FIX display item status if item is checked out

In course reserves, if an item which was added to a course is checked
out, it is not possible to show details for that course on OPAC.
The error says: "Template process failed: undef error - The method
onsite_checkout is not covered by tests! at
/home/koha/src/C4/Templates.pm line 121."

onsite_checkout is an attribute of Koha::Checkout, not Koha::Item

Test plan:
Create a course with 2 items that are checked out (standard and on-site)
At the OPAC, add them to your cart and confirm the status of these 2
items is correct
Confirm that on the detail page of the bib record as well as the detail
of the course.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

koha-tmpl/opac-tmpl/bootstrap/en/includes/item-status.inc

@@ -16,12 +16,16 @@
     [% END %]
 [% END %]
 
-[% IF item.isa('Koha::Item') %][% SET datedue = issue.date_due %]
+[% IF item.isa('Koha::Item') %]
-[% ELSE %][% SET datedue = item.datedue || issue.date_due %]
+    [% SET datedue = issue.date_due %]
+    [% SET onsite_checkout = issue.onsite_checkout %]
+[% ELSE %]
+    [% SET datedue = item.datedue || issue.date_due %]
+    [% SET onsite_checkout = item.onsite_checkout %]
 [% END %]
 [% IF datedue %]
     [% SET itemavailable = 0 %]
-    [% IF item.onsite_checkout %]
+    [% IF onsite_checkout %]
         [% IF ( OPACShowCheckoutName ) %]
             <span class="item-status checkedout">Currently in local use by [% item.firstname %] [% item.surname %] [% IF ( item.cardnumber ) %]([% item.cardnumber %])[% END %]</span>
         [% ELSE %]