[debops.opendkim] Fix Postfix dependent config

Due to changes in the 'parse_kv_items' Ansible filter included in
DebOps, the dependent configuration used in the 'debops.postfix' role
and stored on the Ansible Controller needs to have the 'state' parameter
set explicitly to be correctly merged with other Postfix configuration.

ansible/roles/debops.opendkim/defaults/main.yml

@@ -470,11 +470,13 @@ opendkim__postfix__dependent_maincf:
     value:
       - name: 'unix:/opendkim/opendkim.sock'
         weight: -300
+    state: 'present'
 
   - name: 'non_smtpd_milters'
     value:
       - name: 'unix:/opendkim/opendkim.sock'
         weight: -300
+    state: 'present'
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