dovecot: changes to config aligning to 2.4

data/conf/dovecot/conf.d/25-services.conf

@@ -33,6 +33,15 @@ service config {
   }
 }
 
+# anvil socket
+service anvil {
+  unix_listener anvil {
+    user = vmail
+    group = vmail
+    mode = 0660
+  }
+}
+
 # auth sockets and inet
 service auth {
   inet_listener auth-inet {