Bug 35310: Only show 'Current renewals' link if item is currently checked out

Bug 35310: Only show 'Current renewals' link if item is currently checked out

1) Checkout an item to Koha user, barcode 39999000003192
2) Renew that barcode
3) Visit the items page of the biblio record, click on "View" in front of "Current renewals"
/cgi-bin/koha/catalogue/moredetail.pl?biblionumber=76
4) Notice it shows the renewals as expected
5) Return the same item 39999000003192
6) Repeat 3). Notice it never loads renewals and network console shows HTTP error 400
7) Apply this patch. Repeat the test plan. Notice the 'Current renewals' no longer shows for the item because it is no longer checked out, so whatever past renewals are no longer 'current'

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>