Add possibility to change mdns listening address and port

Change-Id: I5a1f8f53629a1616323f9d3a053d5dddcccdd85c
Related-Bug: https://mirantis.jira.com/browse/PROD-14930
diff --git a/README.rst b/README.rst
index 0192058..9ca7da7 100644
--- a/README.rst
+++ b/README.rst
@@ -43,6 +43,9 @@
           tenant: service
           user: designate
           password: passw0rd
+        mdns:
+          address: 0.0.0.0
+          port: 5354
         message_queue:
           engine: rabbitmq
           members:
@@ -88,6 +91,11 @@
    it defaults to http://*server:bind:api:address*:9001/.
 
 .. note::
+   *server:mdns:address* and *server:mdns:port* options allow to change MDNS listening address and
+   port. Changes to server:pools:*:targets will be also required if the MDNS's address and port are
+   being used there.
+
+.. note::
    *worker:enabled* sets worker role and installs designate-worker and designate-producer packages
    which services will push changes to backend DNS servers.
    *pool_manager:enabled* should be a default role for older releases of OpenStack, older than