Improve keystone.conf [memcache] documentation
Improve keystone.conf [memcache] documentation

Change-Id: I850dd3ec48c1eaba881b4bbca255972c7d8555c5

rajalokan/keystone,rajalokan/keystone,rajalokan/keystone,openstack/keystone,cernops/keystone,ilay09/keystone,cernops/keystone,mahak/keystone,openstack/keystone,ilay09/keystone,ilay09/keystone,mahak/keystone,openstack/keystone,mahak/keystone