Shuffle of the order of BIND9 masters

Make sure that the masters given to BIND9 on an addzone are shuffled
so that different MiniDNS instances are targetted for AXFRs for different
zones

Change-Id: Id01815f8d70fa50e83f0c6bee52894b885788e49
Closes-Bug: 1444414

designate/backend/impl_bind9.py

@@ -13,6 +13,8 @@
 # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 # License for the specific language governing permissions and limitations
 # under the License.
+import random
+
 from oslo_log import log as logging
 
 from designate import exceptions
@@ -42,6 +44,10 @@ class Bind9Backend(base.Backend):
             host = master['host']
             port = master['port']
             masters.append('%s port %s' % (host, port))
+
+        # Ensure different MiniDNS instances are targetted for AXFRs
+        random.shuffle(masters)
+
         rndc_op = [
             'addzone',
             '%s { type slave; masters { %s;}; file "slave.%s%s"; };' %