Correct keystone memcached host setting

keystone was configured to connect to memcached on the host IP
address. Unfortunately, memcached is only listening on localhost,
so this setting actually hurts performance as keystone fails to
connect to the memcached server. There's no indication of this in
the keystone logs since this is just how memcache client works
(ignoring errors).

You can verify this by
1) in /etc/memcached.conf, set -vv
2) restart memcached: service memcached restart
3) watch /var/log/memcached.log
4) There will be no output

with this change, there will be output in /var/log/memcached.log

Also the performance should be a lot better.

Change-Id: I95d798d122e2a95e27eb1d2c4e786c3cd844440b
diff --git a/lib/keystone b/lib/keystone
index c94bcd3..5695004 100644
--- a/lib/keystone
+++ b/lib/keystone
@@ -246,7 +246,7 @@
     # Enable caching
     iniset $KEYSTONE_CONF cache enabled "True"
     iniset $KEYSTONE_CONF cache backend "oslo_cache.memcache_pool"
-    iniset $KEYSTONE_CONF cache memcache_servers $SERVICE_HOST:11211
+    iniset $KEYSTONE_CONF cache memcache_servers localhost:11211
 
     # Do not cache the catalog backend due to https://bugs.launchpad.net/keystone/+bug/1537617
     iniset $KEYSTONE_CONF catalog caching "False"