I manual verify the functional test. It's pass.

```
2024-05-27 03:57:32 [INFO] Deploying bundle '/home/ubuntu/CanonicalProjects/charm-rsyslog-forwarder-ha/tests/functional/tests/bundles/bionic.yaml' on to 'zaza-8b1c328f83d7' model
2024-05-27 03:57:32 [INFO] Rendered template '<Template 'local-charm-overlay.yaml.j2'>' to file '/home/ubuntu/tmpqa0560hb/local-charm-overlay.yaml'
2024-05-27 03:57:32 [INFO] Rendered template '<Template 'bionic.yaml.j2'>' to file '/home/ubuntu/tmpqa0560hb/bionic.yaml'
2024-05-27 03:57:32 [INFO] Deploying overlay '/home/ubuntu/tmpqa0560hb/local-charm-overlay.yaml' on to 'zaza-8b1c328f83d7' model
2024-05-27 03:57:32 [INFO] Deploying overlay '/home/ubuntu/tmpqa0560hb/bionic.yaml' on to 'zaza-8b1c328f83d7' model
2024-05-27 03:57:34 [INFO] Located charm "rsyslog" in charm-hub, channel latest/stable
2024-05-27 03:57:34 [INFO] Located charm "ubuntu" in charm-hub, channel latest/stable
2024-05-27 03:57:34 [INFO] Executing changes:
2024-05-27 03:57:34 [INFO] - upload charm rsyslog from charm-hub for base ubuntu@18.04/stable with architecture=amd64
2024-05-27 03:57:35 [INFO] - deploy application rsyslog from charm-hub on ubuntu@18.04/stable
2024-05-27 03:57:36 [INFO] - upload charm /home/ubuntu/CanonicalProjects/charm-rsyslog-forwarder-ha//rsyslog-forwarder-ha.charm for base ubuntu@18.04/stable with architecture=amd64
2024-05-27 03:57:37 [INFO] - deploy application rsyslog-forwarder-ha on ubuntu@18.04/stable
2024-05-27 03:57:37 [INFO] - upload charm ubuntu from charm-hub for base ubuntu@18.04/stable with architecture=amd64
2024-05-27 03:57:38 [INFO] - deploy application syslog-source from charm-hub on ubuntu@18.04/stable using ubuntu
2024-05-27 03:57:38 [INFO] - add relation rsyslog-forwarder-ha:syslog - rsyslog:aggregator
2024-05-27 03:57:38 [INFO] - add relation rsyslog-forwarder-ha:juju-info - syslog-source:juju-info
2024-05-27 03:57:38 [INFO] - add unit rsyslog/0 to new machine 0
2024-05-27 03:57:38 [INFO] - add unit syslog-source/0 to new machine 1
2024-05-27 03:57:39 [INFO] Deploy of bundle completed.
2024-05-27 03:57:39 [INFO] Waiting for environment to settle
2024-05-27 03:57:39 [INFO] Timeout for deployment to settle set to: 3600
2024-05-27 03:57:39 [INFO] Maximum resolve count for deployment set to: 0
2024-05-27 03:57:39 [INFO] Waiting for application states to reach targeted states.
2024-05-27 03:57:39 [INFO] Waiting for an application to be present
2024-05-27 03:57:39 [INFO] Now checking workload status and status messages
2024-05-27 03:59:41 [INFO] Application syslog-source is ready.
2024-05-27 03:59:43 [INFO] Application rsyslog-forwarder-ha is ready.
2024-05-27 03:59:51 [INFO] Application rsyslog is ready.
2024-05-27 03:59:51 [INFO] All applications reached approved status, number of units (where relevant), and workload status message checks.
2024-05-27 03:59:51 [INFO] Waiting for zaza-8b1c328f83d7 to settle
2024-05-27 03:59:51 [INFO] Model zaza-8b1c328f83d7 has settled
2024-05-27 03:59:51 [INFO] configuring zaza-8b1c328f83d7
2024-05-27 03:59:51 [INFO] Finished configuring zaza-8b1c328f83d7
2024-05-27 03:59:51 [INFO] Testing zaza-8b1c328f83d7
2024-05-27 03:59:51 [INFO] ## Running Test tests.test_rsyslog_forwarder_ha.CharmOperationTest ##
2024-05-27 03:59:51 [INFO] test_01_rsyslog_receiving_data (tests.test_rsyslog_forwarder_ha.CharmOperationTest)
2024-05-27 03:59:51 [INFO] Verify if the API is ready.
2024-05-27 03:59:51 [INFO]  ... 
2024-05-27 03:59:53 [INFO] ok
2024-05-27 03:59:53 [INFO] ----------------------------------------------------------------------
2024-05-27 03:59:53 [INFO] Ran 1 test in 2.212s
2024-05-27 03:59:53 [INFO] OK
2024-05-27 03:59:53 [INFO] Finished testing zaza-8b1c328f83d7
2024-05-27 03:59:53 [INFO] Destroying model zaza-8b1c328f83d7
```