* It will allow to configure horizon cache
backend and its options in local_settings.py
* Add tests for cache_backend and cache_options
* Change default value of cache_server_ip to undef.
At the moment master of horizon has default value of backend
to: django.core.cache.backends.locmem.LocMemCache [0]
while our template generates config with default:
django.core.cache.backends.memcached.MemcachedCache
[0] http://docs.openstack.org/developer/horizon/topics/deployment.html
Change-Id: I7484727fd2af26d47bc0f59e59b7f6f75daf1092
Related-Bug: #1441522