Infinite log message loop "Error while deleting router" in neutron L3 agent logs in Red Hat OpenStack Platform

Issue

Neutron L3 agent infinitely logs error message Error while deleting router in Red Hat OpenStack Platform.

From /var/log/neutron/l3-agent.log:

2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent [-] Error while deleting router <UUID>
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent Traceback (most recent call last):
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/agent.py", line 381, in _safe_router_removed
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     self._router_removed(router_id)
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/agent.py", line 399, in _router_removed
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     ri.delete(self)
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/ha_router.py", line 414, in delete
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     self.destroy_state_change_monitor(self.process_monitor)
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/ha_router.py", line 356, in destroy_state_change_monitor
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     pm = self._get_state_change_monitor_process_manager()
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/ha_router.py", line 327, in _get_state_change_monitor_process_manager
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     default_cmd_callback=self._get_state_change_monitor_callback())
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/ha_router.py", line 330, in _get_state_change_monitor_callback
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     ha_device = self.get_ha_device_name()
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/ha_router.py", line 168, in get_ha_device_name
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     return (HA_DEV_PREFIX + self.ha_port['id'])[:self.driver.DEV_NAME_LEN]
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent TypeError: 'NoneType' object has no attribute '__getitem__'
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent 
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent [-] Error while deleting router <UUID>
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent Traceback (most recent call last):
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/agent.py", line 381, in _safe_router_removed
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     self._router_removed(router_id)
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/agent.py", line 399, in _router_removed
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     ri.delete(self)
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/ha_router.py", line 414, in delete
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     self.destroy_state_change_monitor(self.process_monitor)
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/ha_router.py", line 356, in destroy_state_change_monitor
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     pm = self._get_state_change_monitor_process_manager()
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/ha_router.py", line 327, in _get_state_change_monitor_process_manager
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     default_cmd_callback=self._get_state_change_monitor_callback())
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/ha_router.py", line 330, in _get_state_change_monitor_callback
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     ha_device = self.get_ha_device_name()
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent   File "/usr/lib/python2.7/site-packages/neutron/agent/l3/ha_router.py", line 168, in get_ha_device_name
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent     return (HA_DEV_PREFIX + self.ha_port['id'])[:self.driver.DEV_NAME_LEN]
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent TypeError: 'NoneType' object has no attribute '__getitem__'
2018-01-03 13:49:48.205 24327 ERROR neutron.agent.l3.agent