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/heat/server/cluster.yml b/heat/server/cluster.yml
index 8e38f4f..5829aee 100644
--- a/heat/server/cluster.yml
+++ b/heat/server/cluster.yml
@@ -5,7 +5,8 @@
 - system.haproxy.proxy.listen.openstack.heat
 parameters:
   _param:
-    cluster_public_protocol: https
+    cluster_public_protocol: 'https'
+    cluster_internal_protocol: 'http'
   linux:
     system:
       package:
@@ -54,6 +55,7 @@
         tenant: service
         user: heat
         password: ${_param:keystone_heat_password}
+        protocol: ${_param:cluster_internal_protocol}
       message_queue:
         engine: rabbitmq
         port: 5672