[RFE] Alert when logs contain "operator must manually delete" messages

When auditing Octavia due to looping amphora failovers, it was discovered that there is a log entry which states:

2021-11-16 16:13:16.412 497882 WARNING octavia.controller.healthmanager.health_drivers.update_db [-] The amphora c4d4741d-91f8-40f6-9059-28eec8510180 with IP fc00:b78c:ae27:af5e:f816:3eff:fe78:8c53 is missing from the DB, so it cannot be automatically deleted (the compute_id is unknown). An operator must manually delete it from the compute service.

It would be helpful if "operator action required" messages such as these in the octavia-health-manager.log could be exposed via Nagios checks.