Centralize setting internal_protocol

Internal Openstack APIs may be encrypted with https. This patch
centralize setting internal API protocol among services by
setting one of depending if cluster or single models are used:
  cluster_internal_protocol: 'https'
  internal_protocol: 'https'

Change-Id: I2baff79cd5851678559d7de47460fdd2031f70ee
diff --git a/designate/server/single.yml b/designate/server/single.yml
index 765dcf8..3fdd448 100644
--- a/designate/server/single.yml
+++ b/designate/server/single.yml
@@ -3,6 +3,7 @@
 parameters:
   _param:
     designate_admin_api_enabled: false
+    internal_protocol: 'http'
   linux:
     system:
       package:
@@ -38,6 +39,7 @@
         tenant: service
         user: designate
         password: ${_param:keystone_designate_password}
+        protocol: ${_param:internal_protocol}
       message_queue:
         engine: rabbitmq
         host: ${_param:cluster_vip_address}