Bug 36276: Fix editing of identity provider and domains

Bug 36276: Fix editing of identity provider and domains

This patch fixes identity_providers.pl to remove the "cud-" prefix for
two operations which are not POSTed: editing identity providers and
editing domains.

To test, apply the patch and restart services.

- Go to Administration -> Identity providers.
- If necessary, create an identity provider and then click "Manage
  domains" -> New identity provider domain to create a new domain.
- From the list of domains, click "Edit"
- The edit form should appear with all the correct details prefilled.
  - Check that the page title, breadcrumbs, and page header all show the
    correct domain.
  - Make a change to the domain and confirm that the changes are saved.

- From the list of identity providers, click "Edit"
- This form should also load correctly.
- Submitted changes should be saved correctly.

Sponsored-by: Athens County Public Libraries
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>