Fix order of operations in api payload

PDNS checks that when a `CNAME` rrset is created that no other rrset of
the same name but a different rtype exists. When changing a record type
to `CNAME`, PDA will send two operations in one api call to PDNS: A
deletion of the old rrset, and the addition of the new rrset. For the
check in PDNS to pass, the deletion needs to happen before the addition.
Before PR #1201 that was the case, the first api call did deletions and
the second handled additions and changes. Currently the api payload
contains additions first and deletions last. PDNS applies these in the
order they are passed in the payload to the api, so to restore the
original/correct/working behaviour the order of operations in the api
payload has to be reversed.

fixes #1251

powerdnsadmin/models/record.py

@@ -337,7 +337,8 @@ class Record(object):
         replaces = [replace_for_api(r) for r in new_rrsets]
         deletes = [delete_for_api(r) for r in del_rrsets if not rrset_in(r, replaces)]
         return {
-            'rrsets': replaces + deletes
+            # order matters: first deletions, then additions+changes
+            'rrsets': deletes + replaces
         }
 
     def apply(self, domain_name, submitted_records):