Add default for ceph_ansible_playbook in update/upgrade prepare workflow
Add default for ceph_ansible_playbook in update/upgrade prepare workflow

The end goal here is to remove it completely, but there's a
chicken-and-egg issue between removing it from tripleoclient and
tripleo-common. First we default it here, then we remove it from
tripleoclient, then we remove it here.

Partial-Bug: #1783949
Change-Id: If80f9cc2f4cb32610dc5eb87159872e28363a21a

openstack/tripleo-common,openstack/tripleo-common