[BACKPORT][v1.6.1][BUG] Use config map to update `default-replica-count` won't apply to `default-replica-count.definition.default` if the value equal to current `default-replica-count.value` about longhorn HOT 2 CLOSED

Pre Ready-For-Testing Checklist

• Where is the reproduce steps/test steps documented?
  The reproduce steps/test steps are at: See base issue #7755

• Is there a workaround for the issue? If so, where is it documented?
  The workaround is at:

• Does the PR include the explanation for the fix or the feature?

from longhorn.

Verified on v1.6.1-rc1 20240314

• longhorn v1.6.1-rc1 6e96e27

The test steps
#7755 (comment)

Result Passed

1. Deploy Longhorn(master-head, v1.6.1-rc1)

2. Update default-replica-count to 4 by UI or by kubectl
kubectl -n longhorn-system patch -p '{"value": "4"}' --type=merge lhs default-replica-count

3. From API, the value: 4, definition.default: 3
   

4. Apply below yaml to update default replica count to 4 by config map

   apiVersion: v1
   data:
     default-setting.yaml: |
       default-replica-count: 4
       priority-class: longhorn-critical
   kind: ConfigMap
   metadata:
     name: longhorn-default-setting
     namespace: longhorn-system
   

5. Kubectl replied configmap/longhorn-default-setting configured, Can see both definition.default and value updated to 4

   > k apply -f update_default_replica.yaml
   configmap/longhorn-default-setting configured
   

   

6. Apply below yaml to update default replica count to 5 by config map

   apiVersion: v1
   data:
     default-setting.yaml: |
       default-replica-count: 5
       priority-class: longhorn-critical
   kind: ConfigMap
   metadata:
     name: longhorn-default-setting
     namespace: longhorn-system
   

7. Can see both definition.default and value updated to 5

from longhorn.