Fluentbit: Add Decode_Field_As config to docker parser

This adds the Decode_Field_As configuration key to the docker
parser for fluentbit. This is required to escape utf-8 encoded
characters appropriately in the log field

Change-Id: Ie2600cfe22045e3ab651fddf61ed2f676ab8a1d5

fluent-logging/values.yaml

@@ -200,6 +200,7 @@ conf:
         Time_Key: time
         Time_Format: "%Y-%m-%dT%H:%M:%S.%L"
         Time_Keep: On
+        Decode_Field_As: escaped_utf8 log
   fluentd:
     - metrics_agent:
         header: source