Multi backend attepts to read a deleted domain

This effectively results in all delete-domain requests failing when
the multi backend is used.

Closes-Bug: 1375397
Change-Id: I05a54600bf7493ff467b8f5a81af7d682fe5ca7a

designate/backend/impl_multi.py

@@ -106,10 +106,13 @@ class MultiBackend(base.Backend):
         self.master.update_domain(context, domain)
 
     def delete_domain(self, context, domain):
-        # Get the "full" domain (including id) from Central first, as we may
+        # Fetch the full domain from Central first, as we may
         # have to recreate it on slave if delete on master fails
+        deleted_context = context.deepcopy()
+        deleted_context.show_deleted = True
+
         full_domain = self.central.find_domain(
-            context, {'name': domain['name']})
+            deleted_context, {'id': domain['id']})
 
         self.slave.delete_domain(context, domain)
         try:

designate/tests/test_backend/test_multi.py

@@ -103,6 +103,7 @@ class MultiBackendTestCase(tests.TestCase, BackendTestMixin):
     def test_delete_domain(self):
         context = self.get_context()
         domain = self.get_domain_fixture()
+        domain['id'] = 'a8aeb2ee-40da-476b-a9d8-26bf0c0065f6'
 
         # Since multi's delete fetches the domain from central to be able to
         # recreate it if something goes wrong, create the domain first