Disable memcached

We want to disable memcached until we patch availability_zones.py [1]

[1] https://review.openstack.org/#/c/41873/
Merge pull request #59 from blueboxgroup/disable-memcached

I am going to merge this.  I don't want to take the chance that memcached gets re-enabled in BFG accidentally.  Tim had ok'ed me making this change earlier today.