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
(cherry picked from commit 75ace7a5edbb6496633b97dc1d6b60e000ff3e5f)