Description of problem:

FFU: controllers upgrade fails on TASK [tripleo-ssh-known-hosts : Add hosts key in /etc/ssh/ssh_known_hosts for live/cold-migration] 

 u'PLAY [Common roles for TripleO servers] ****************************************',
 u'',
 u'TASK [tripleo-bootstrap : Deploy required packages to bootstrap TripleO] *******',
 u'Monday 20 August 2018  11:18:53 -0400 (0:00:00.106)       0:00:04.688 ********* ',
 u'ok: [controller-r02-00] => {"changed": false, "failed": false, "msg": "", "rc": 0, "results": ["openstack-heat-agents-1.5.4-0.20180308153305.ecf43c7.el7ost.noarch providing openstack-heat-agents is already installed", "jq-1.3-4.el7ost.x86_64 providing jq is already installed"]}',
 u'ok: [controller-r00-00] => {"changed": false, "failed": false, "msg": "", "rc": 0, "results": ["openstack-heat-agents-1.5.4-0.20180308153305.ecf43c7.el7ost.noarch providing openstack-heat-agents is already installed", "jq-1.3-4.el7ost.x86_64 providing jq is already installed"]}',
 u'ok: [controller-r01-00] => {"changed": false, "failed": false, "msg": "", "rc": 0, "results": ["openstack-heat-agents-1.5.4-0.20180308153305.ecf43c7.el7ost.noarch providing openstack-heat-agents is already installed", "jq-1.3-4.el7ost.x86_64 providing jq is already installed"]}',
 u'',
 u'TASK [tripleo-bootstrap : Create /var/lib/heat-config/tripleo-config-download directory for deployment data] ***',
 u'Monday 20 August 2018  11:18:54 -0400 (0:00:00.796)       0:00:05.485 ********* ',
 u'changed: [controller-r02-00] => {"changed": true, "failed": false, "gid": 0, "group": "root", "mode": "0755", "owner": "root", "path": "/var/lib/heat-config/tripleo-config-download", "secontext": "unconfined_u:object_r:var_lib_t:s0", "size": 6, "state": "directory", "uid": 0}',
 u'changed: [controller-r01-00] => {"changed": true, "failed": false, "gid": 0, "group": "root", "mode": "0755", "owner": "root", "path": "/var/lib/heat-config/tripleo-config-download", "secontext": "unconfined_u:object_r:var_lib_t:s0", "size": 6, "state": "directory", "uid": 0}',
 u'changed: [controller-r00-00] => {"changed": true, "failed": false, "gid": 0, "group": "root", "mode": "0755", "owner": "root", "path": "/var/lib/heat-config/tripleo-config-download", "secontext": "unconfined_u:object_r:var_lib_t:s0", "size": 6, "state": "directory", "uid": 0}',
 u'',
 u'TASK [tripleo-ssh-known-hosts : Add hosts key in /etc/ssh/ssh_known_hosts for live/cold-migration] ***',
 u'Monday 20 August 2018  11:18:55 -0400 (0:00:00.380)       0:00:05.865 ********* ',
 u'fatal: [controller-r01-00]: FAILED! => {"failed": true, "msg": "The task includes an option with an undefined variable. The error was: \'dict object\' has no attribute u\'controller-r01-00\'\\n\\nThe error appears to have been in \'/usr/share/ansible/roles/tripleo-ssh-known-hosts/tasks/main.yml\': line 2, column 3, but may\\nbe elsewhere in the file depending on the exact syntax problem.\\n\\nThe offending line appears to be:\\n\\n---\\n- name: Add hosts key in /etc/ssh/ssh_known_hosts for live/cold-migration\\n  ^ here\\n\\nexception type: <class \'ansible.errors.AnsibleUndefinedVariable\'>\\nexception: \'dict object\' has no attribute u\'controller-r01-00\'"}',
 u'fatal: [controller-r02-00]: FAILED! => {"failed": true, "msg": "The task includes an option with an undefined variable. The error was: \'dict object\' has no attribute u\'controller-r01-00\'\\n\\nThe error appears to have been in \'/usr/share/ansible/roles/tripleo-ssh-known-hosts/tasks/main.yml\': line 2, column 3, but may\\nbe elsewhere in the file depending on the exact syntax problem.\\n\\nThe offending line appears to be:\\n\\n---\\n- name: Add hosts key in /etc/ssh/ssh_known_hosts for live/cold-migration\\n  ^ here\\n\\nexception type: <class \'ansible.errors.AnsibleUndefinedVariable\'>\\nexception: \'dict object\' has no attribute u\'controller-r01-00\'"}',
 u'fatal: [controller-r00-00]: FAILED! => {"failed": true, "msg": "The task includes an option with an undefined variable. The error was: \'dict object\' has no attribute u\'controller-r01-00\'\\n\\nThe error appears to have been in \'/usr/share/ansible/roles/tripleo-ssh-known-hosts/tasks/main.yml\': line 2, column 3, but may\\nbe elsewhere in the file depending on the exact syntax problem.\\n\\nThe offending line appears to be:\\n\\n---\\n- name: Add hosts key in /etc/ssh/ssh_known_hosts for live/cold-migration\\n  ^ here\\n\\nexception type: <class \'ansible.errors.AnsibleUndefinedVariable\'>\\nexception: \'dict object\' has no attribute u\'controller-r01-00\'"}',
 u'',
 u'NO MORE HOSTS LEFT *************************************************************',
 u'',
 u'PLAY RECAP *********************************************************************',
 u'controller-r00-00          : ok=4    changed=1    unreachable=0    failed=1   ',
 u'controller-r01-00          : ok=4    changed=1    unreachable=0    failed=1   ',
 u'controller-r02-00          : ok=4    changed=1    unreachable=0    failed=1   ',
 u'',
 u'Monday 20 August 2018  11:18:55 -0400 (0:00:00.107)       0:00:05.972 ********* ',
 u'=============================================================================== ']

Version-Release number of selected component (if applicable):
puddle 2018-08-16.1

How reproducible:
1/1

Steps to Reproduce:
1. Deploy OSP10 with 3 controller + 2 compute + 3 ceph node with following custom hostnames:

parameter_defaults:
    HostnameMap:
        ceph-0: CEPH-R00-00
        ceph-1: CEPH-R01-00
        ceph-2: CEPH-R02-00
        compute-0: COMPUTE-R00-00
        compute-1: COMPUTE-R01-00
        controller-0: CONTROLLER-R00-00
        controller-1: CONTROLLER-R01-00
        controller-2: CONTROLLER-R02-00

Actual results:

openstack overcloud upgrade run --roles Controller --skip-tags validation fails on TASK [tripleo-ssh-known-hosts : Add hosts key in /etc/ssh/ssh_known_hosts for live/cold-migration]

Expected results:
No failure.

Additional info: