Using list of urls for memcached

Memcached is being deployed with PetSet, so we can use
list of memcached server urls in configs

Change-Id: I975ae97796df3ba28297cfdc2706324e30380523
Depends-On: Idbcb504b23deba33f33b48ce69a4e643b6fc4cf4

service/files/local_settings.j2

@@ -129,7 +129,7 @@ SECRET_KEY = "{{ horizon.secret_key }}"
 CACHES = {
     'default': {
         'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
-        'LOCATION': '{{ address("memcached") }}:{{ memcached.port.cont }}',
+        'LOCATION': '{{ address("memcached", memcached.port, multiple=True) | join(";") }}',
     },
 }