Ceilometer API service fails to open listening port

Issue

• When the openstack-ceilometer-api endpoint launches it fails to open a listening port.
• The service is active, but there is no port in the output of netstat.

[jenkins@controller ~]$ sudo systemctl status -l openstack-ceilometer-api
openstack-ceilometer-api.service - OpenStack ceilometer API service
   Loaded: loaded (/usr/lib/systemd/system/openstack-ceilometer-api.service; enabled)
   Active: active (running) since Mon 2016-05-23 20:37:47 UTC; 17h ago
 Main PID: 10865 (ceilometer-api)
   CGroup: /system.slice/openstack-ceilometer-api.service
           └─10865 /usr/bin/python /usr/bin/ceilometer-api --logfile /var/log/ceilometer/api.log

May 23 20:37:47 controller systemd[1]: Started OpenStack ceilometer API service.
May 23 20:37:48 controller ceilometer-api[10865]: /usr/lib64/python2.7/site-packages/pymongo/mongo_client.py:343: UserWarning: database name or authSource in URI is being ignored. If you wish to authenticate to ceilometer, you must provide a username and password.
May 23 20:37:48 controller ceilometer-api[10865]: "must provide a username and password." % (db_name,))

• Ceilometer was previously working