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/panko.yml b/nginx/server/proxy/openstack/panko.yml
index 6081dd1..45d389b 100644
--- a/nginx/server/proxy/openstack/panko.yml
+++ b/nginx/server/proxy/openstack/panko.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_panko_host: ${_param:panko_service_host}
+    nginx_proxy_openstack_panko_protocol: 'http'
   nginx:
     server:
       enabled: true
@@ -15,7 +16,7 @@
           proxy:
             host: ${_param:nginx_proxy_openstack_panko_host}
             port: 8977
-            protocol: http
+            protocol: ${_param:nginx_proxy_openstack_panko_protocol}
           host:
             name: ${_param:nginx_proxy_openstack_api_host}
             port: 8977