rhel-osp-director: 7.2GA->7.3 async fails "Error: Could not find data item mysql_clustercheck_password in any Hiera data file and no default supplied at /var/lib/heat-config/heat-config-puppet/3b5aaa9f-1309-4b85-a590-5fa96de9b9d2.pp:454 on node overcloud-controller-1.localdomain"

Environment:
openstack-tripleo-heat-templates-0.8.6-127.el7ost.noarch
openstack-puppet-modules-2015.1.8-51.el7ost.noarch
instack-undercloud-2.1.2-39.el7ost.noarch

Steps to reproduce:
1. Deploy 7.2GA with:
openstack overcloud deploy --templates --control-scale 3 --compute-scale 1 --neutron-network-type vxlan --neutron-tunnel-types vxlan --ntp-server clock.redhat.com --timeout 90 -e /usr/share/openstack-tripleo-heat-templates/environments/storage-environment.yaml -e /usr/share/openstack-tripleo-heat-templates/environments/network-isolation.yaml -e network-environment.yaml --ceph-storage-scale 1

2. Update the undercloud to 7.3async

3. To work around https://bugzilla.redhat.com/show_bug.cgi?id=1344794, 
Append the line: "default: ''" under MysqlClustercheckPassword stanza.

4. Attempt to update the overcloud to 7.3async with:
openstack overcloud update stack overcloud -i --templates -e /usr/share/openstack-tripleo-heat-templates/overcloud-resource-registry-puppet.yaml -e /usr/share/openstack-tripleo-heat-templates/environments/storage-environment.yaml -e /usr/share/openstack-tripleo-heat-templates/environments/network-isolation.yaml    -e network-environment.yaml


Result:
The update fails.
IN_PROGRESS
FAILED
update finished with status FAILED


[stack@instack ~]$ heat deployment-show a12f7dc7-2193-4297-8beb-8776cb435b1c
{
  "status": "FAILED",
  "server_id": "a015d08f-b005-4a22-ba78-b3e71e59d870",
  "config_id": "0fe8e61b-a47a-434e-a993-92fd69201fcd",
  "output_values": {
    "deploy_stdout": "",
    "deploy_stderr": "Device \"br_ex\" does not exist.\nDevice \"br_int\" does not exist.\nDevice \"br_tun\" does not exist.\nDevice \"ovs_system\" does not exist.\n\u001b[1;31mError: Could not find data item mysql_clustercheck_password in any Hiera data file and no default supplied at /var/lib/heat-config/heat-config-puppet/0fe8e61b-a47a-434e-a993-92fd69201fcd.pp:454 on node overcloud-controller-0.localdomain\u001b[0m\n\u001b[1;31mError: Could not find data item mysql_clustercheck_password in any Hiera data file and no default supplied at /var/lib/heat-config/heat-config-puppet/0fe8e61b-a47a-434e-a993-92fd69201fcd.pp:454 on node overcloud-controller-0.localdomain\u001b[0m\n",
    "deploy_status_code": 1
  },
  "creation_time": "2016-07-05T15:01:37Z",
  "updated_time": "2016-07-05T18:57:58Z",
  "input_values": {},
  "action": "UPDATE",
  "status_reason": "deploy_status_code : Deployment exited with non-zero status code: 1",
  "id": "a12f7dc7-2193-4297-8beb-8776cb435b1c"
}


Expected result:
Successful update.