Enable LDAP as a keystone backend (bnc#785470)

Therefore, changing the identity driver is necessary.  Templatize LDAP
configuration in the chef recipe. There are too many values to present
them in the UI in any meaningful way.
Merge pull request #100 from saschpe/release/pebbles/master-ldap

Enable LDAP as a keystone backend (bnc#785470)