Comment 5 for bug 1755485

For the record, it seems I'm hitting the same problem in test "tripleo-ci-centos-7-3nodes-multinode" when gating tripleo-heat-templates.

This is apparently not limited to my review, e.g.:
  . https://review.openstack.org/#/c/539503/
  . https://review.openstack.org/#/c/547476/

I don't have other t-h-t example right now but both reviews above fail like:
2018-03-20 18:23:27,063 23530 ERROR [tempest.lib.common.ssh] Failed to establish authenticated ssh connection to cirros@192.168.24.107 after 23 attempts
2018-03-20 18:23:27.063 23530 ERROR tempest.lib.common.ssh Traceback (most recent call last):
2018-03-20 18:23:27.063 23530 ERROR tempest.lib.common.ssh File "/usr/lib/python2.7/site-packages/tempest/lib/common/ssh.py", line 107, in _get_ssh_connection
2018-03-20 18:23:27.063 23530 ERROR tempest.lib.common.ssh sock=proxy_chan)
2018-03-20 18:23:27.063 23530 ERROR tempest.lib.common.ssh File "/usr/lib/python2.7/site-packages/paramiko/client.py", line 380, in connect
2018-03-20 18:23:27.063 23530 ERROR tempest.lib.common.ssh look_for_keys, gss_auth, gss_kex, gss_deleg_creds, gss_host)
2018-03-20 18:23:27.063 23530 ERROR tempest.lib.common.ssh File "/usr/lib/python2.7/site-packages/paramiko/client.py", line 621, in _auth
2018-03-20 18:23:27.063 23530 ERROR tempest.lib.common.ssh raise saved_exception
2018-03-20 18:23:27.063 23530 ERROR tempest.lib.common.ssh AuthenticationException: Authentication failed.
2018-03-20 18:23:27.063 23530 ERROR tempest.lib.common.ssh
2018-03-20 18:23:27,066 23530 ERROR [tempest.scenario.manager] Public network connectivity check failed
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager Traceback (most recent call last):
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager File "/usr/lib/python2.7/site-packages/tempest/scenario/manager.py", line 585, in check_public_network_connectivity
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager mtu=mtu)
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager File "/usr/lib/python2.7/site-packages/tempest/scenario/manager.py", line 571, in check_vm_connectivity
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager self.get_remote_client(ip_address, username, private_key)
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager File "/usr/lib/python2.7/site-packages/tempest/scenario/manager.py", line 358, in get_remote_client
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager linux_client.validate_authentication()
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager File "/usr/lib/python2.7/site-packages/tempest/lib/common/utils/linux/remote_client.py", line 60, in wrapper
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager six.reraise(*original_exception)
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager File "/usr/lib/python2.7/site-packages/tempest/lib/common/utils/linux/remote_client.py", line 33, in wrapper
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager return function(self, *args, **kwargs)
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager File "/usr/lib/python2.7/site-packages/tempest/lib/common/utils/linux/remote_client.py", line 116, in validate_authentication
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager self.ssh_client.test_connection_auth()
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager File "/usr/lib/python2.7/site-packages/tempest/lib/common/ssh.py", line 207, in test_connection_auth
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager connection = self._get_ssh_connection()
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager File "/usr/lib/python2.7/site-packages/tempest/lib/common/ssh.py", line 121, in _get_ssh_connection
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager password=self.password)
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager SSHTimeout: Connection to the 192.168.24.107 via SSH timed out.
2018-03-20 18:23:27.066 23530 ERROR tempest.scenario.manager User: cirros, Password: None