Add purge fetch_directory workaround to deploy.sh
Add purge fetch_directory workaround to deploy.sh

- ceph-ansible expects the fetch directory to be purged for each run
- this workaround ensures it is purged provided deploy.sh is used
- correct fix will probably be to add mistral action to mktmp/rmtmp
- then update https://review.openstack.org/#/c/469644 to call action
- then publish result for use by ansible-playbook as argument

fultonj/tripleo-ceph-ansible,fultonj/tripleo-ceph-ansible