change: add service_type field to dpkg log collection

templates/filebeat.yml.j2

@@ -33,7 +33,8 @@ filebeat.inputs:
   paths:
     - /var/log/dpkg.log
   fields:
-    source_app: "dpkg"
+     service_type: "dpkg"
+  fields_under_root: true
 
 # ================================== Outputs ===================================
 # ------------------------------ Logstash Output -------------------------------