After FFU from 13 to 16.1 post validation is failing because tripleo_ceilometer_agent_central_healthcheck.service is failing to start

Issue

• After FFU from 13 to 16.1 post validation is failing because tripleo_ceilometer_agent_central_healthcheck.service is failing to start.

• Here we see the service-status validations failing:

(undercloud) [stack@undercloud ~]$ openstack tripleo validator run --group post-upgrade
Running Validations without Overcloud settings.
+--------------------------------------+---------------------------+--------+--------------------------+-----------------------------------------------------------------------------------------------------------+-------------------+-------------+
|                 UUID                 |        Validations        | Status |        Host_Group        |                                               Status_by_Host                                              | Unreachable_Hosts |   Duration  |
+--------------------------------------+---------------------------+--------+--------------------------+-----------------------------------------------------------------------------------------------------------+-------------------+-------------+
| 237fd52a-e59c-4dc2-b2b4-45b48b9d2ff5 |       service-status      | FAILED |           all            | overcloud-compute50, overcloud-compute51, overcloud-control50, overcloud-control51, overcloud-control52, undercloud |                   | 0:00:09.576 |
|

• Showing the details of the validations shows tripleo_ceilometer_agent_central_healthcheck failed to start:

(undercloud) [stack@undercloud ~]$ openstack tripleo validator show run --full 237fd52a-e59c-4dc2-b2b4-45b48b9d2ff5

"msg": "The following services failed ['tripleo_ceilometer_agent_central_healthcheck.service loaded failed failed ceilometer_agent_central healthcheck', 
'tripleo_ceilometer_agent_notification_healthcheck.service loaded failed failed ceilometer_agent_notification healthcheck', 
'tripleo_gnocchi_statsd_healthcheck.service loaded failed failed gnocchi_statsd healthcheck               ']"