fixed authenticator to notify each zone only once

issue #1

certbot_pdns/PdnsApiAuthenticator.py

         res = self.api.replace_record(zone["name"], "_acme-challenge." + domain + ".", "TXT", 1, "\"" + token + "\"", False, False)
         if res is not None:
             raise errors.PluginError("Bad return from PDNS API when adding record: %s" % res)
+
+        return response
+
+    def perform_notify(self, zone):
+        logger.info("Notifying zone %s..." % zone["name"])
+
         self.update_soa(zone["name"])
         self.flush_zone(zone["name"])
         self.notify_zone(zone["name"])
 
-        return response
-
     def wait_for_propagation(self, achalls):
         # TODO search zones authoritative servers and check for TXT record on each of them
         # raw_input('Press <ENTER> to continue')

certbot_pdns/authenticator.py

         pass
 
     def perform(self, achalls):  # pylint: disable=missing-docstring
-        responses = [self._perform_single(achall) for achall in achalls]
+        responses = []
+        zones = []
+        for achall in achalls:
+            response, validation = achall.response_and_validation()
+            resp = self.backend.perform_single(achall, response, validation)
+            responses.append(resp)
+
+            domain = achall.domain
+            zone = self.backend.find_best_matching_zone(domain)
+            if zone not in zones:
+                zones.append(zone)
+
+        for zone in zones:
+            self.backend.perform_notify(zone)
+
         self.backend.wait_for_propagation(achalls)
         return responses
 
-    def _perform_single(self, achall):
-        response, validation = achall.response_and_validation()
-        return self.backend.perform_single(achall, response, validation)
-
     def cleanup(self, achalls):  # pylint: disable=missing-docstring
         for achall in achalls:
             self.backend.cleanup(achall)