HA'ed nova consoleauth

By adding memcached_servers to nova.conf this allows consoleauth
to share tokens accross multiple running processes.

    # Consoleauth tokens in memcached
    memcached_servers=172.16.0.44:11211,172.16.0.51:11211

I am not happy with this commit.  I would rather use the default
role var, which allows inventory to override the defaults.  Maybe
someone can give me a hand.