Unhardcode nginx proxy backend portocol for openstack

This patch unhardcode backend protocol for nginx openstack services.

Change-Id: I79f86a0f71c0c3d686027df20ea40253f2426ac3
diff --git a/nginx/server/proxy/openstack/placement.yml b/nginx/server/proxy/openstack/placement.yml
index eda272c..9e8b08c 100644
--- a/nginx/server/proxy/openstack/placement.yml
+++ b/nginx/server/proxy/openstack/placement.yml
@@ -3,6 +3,7 @@
     nginx_proxy_openstack_api_host: ${_param:cluster_public_host}
     nginx_proxy_openstack_api_address: 0.0.0.0
     nginx_proxy_openstack_placement_host: ${_param:placement_service_host}
+    nginx_proxy_openstack_placement_protocol: 'http'
   nginx:
     server:
       enabled: true
@@ -14,7 +15,7 @@
           proxy:
             host: ${_param:nginx_proxy_openstack_placement_host}
             port: 8778
-            protocol: http
+            protocol: ${_param:nginx_proxy_openstack_placement_protocol}
           host:
             name: ${_param:nginx_proxy_openstack_api_host}
             port: 8778