Adds ability to set backends via attributes

* Also adds memcache servers attribute
Use chef role search and bind interface for memcache
case statement syntax mistake fixed
case statement syntax mistake fixed now for realz
Use openstack-common memcached_servers call
Merge pull request #39 from jaypipes/wlan

Adds ability to use different backends for different Keystone components
Merge branch 'master' of github.com:att-cloud/cookbook-keystone into add_syslog

Conflicts:
	templates/default/keystone.conf.erb