Bug 38325: Cannot delete invoice while viewing it

Bug 38325: Cannot delete invoice while viewing it

The link to delete while viewing an individual invoice needs to be updated to
use submit-form-link so it can POST with op='cud-delete'.

Test plan:
 1. Home - Acquisitions, click Search with an empty Vendor: input
 2. Click Receive shipments, enter a number in the Vendor invoice input,
    click Next
 3. In the left sidebar, click Invoices, click Search without any parameters
 4. In the row for your invoice, click the invoice number link
 5. Next to the Save button, click the Delete link, click OK in the
    confirmation alert
 6. You'll see the page reload, and the URL change to include ?op=delete,
    but your invoice remains undeleted.
 7. Apply patch, reload the page
 8. Click Delete, click OK in the confirmation alert
 9. Click Search with no parameters, just to make sure the message about
    "Sorry, but there are no results for your search" really truly means
    that your invoice was deleted and now you don't have any invoices

Sponsored-by: Chetco Community Public Library
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>