Add test coverage for update: SOA and NS managed records

1) "test_admin_updates_soa_and_ns_recordsets"
  Admin uses "x-designate-edit-managed-records" header
  to update SOA and NS records.
  Expected: update request is getting blocked by the API

Change-Id: I4f60dfe62cfae4ffe658fc71d85cd2130054c89f
4 files changed