Set UTC timezone when configuring @timestamp

Author: mdelapenya

x-pack/filebeat/module/shorewall/log/ingest/pipeline.json

@@ -15,6 +15,7 @@
                 "field": "timestamp",
                 "target_field": "@timestamp",
                 "formats": ["MMM dd HH:mm:ss"],
+                "timezone": "UTC",
                 "ignore_failure": false
             }
         },