openstack overcloud update converge" fails with file not found: /etc/ceph/ceph.mon.keyring

Issue

The stack update from OSP13 to the OSP13 latest version failed.

on heat-engine.log show ceph_install error:

2019-04-07 13:04:03.537 13479 ERROR heat.engine.resource     return self._check_action(self.CREATE, execution_id)
2019-04-07 13:04:03.537 13479 ERROR heat.engine.resource   File "/usr/lib/python2.7/site-packages/heat/engine/resources/openstack/mistral/external_resource.py", line 204, in _check_action
2019-04-07 13:04:03.537 13479 ERROR heat.engine.resource     success, output = self._check_execution(action, execution_id)
2019-04-07 13:04:03.537 13479 ERROR heat.engine.resource   File "/usr/lib/python2.7/site-packages/heat/engine/resources/openstack/mistral/external_resource.py", line 171, in _check_execution
2019-04-07 13:04:03.537 13479 ERROR heat.engine.resource     action=action)
2019-04-07 13:04:03.537 13479 ERROR heat.engine.resource ResourceFailure: resources.WorkflowTasks_Step2_Execution: Failure caused by error in tasks: ceph_base_ansible_workflow
2019-04-07 13:04:03.537 13479 ERROR heat.engine.resource 
2019-04-07 13:04:03.537 13479 ERROR heat.engine.resource   ceph_base_ansible_workflow [task_ex_id=3bcc7b7a-87c0-4f39-8d1b-df2802c2603f] -> Failure caused by error in tasks: ceph_install
2019-04-07 13:04:03.537 13479 ERROR heat.engine.resource 
2019-04-07 13:04:03.537 13479 ERROR heat.engine.resource   ceph_install [task_ex_id=86629806-b0bd-46f7-be7e-f303989c228d]