@Chris L The Ambari Agent is a python process so uses Python's logging facility. To change the pattern, go to /etc/ambari-agent/conf and copy logging.conf.sample to logging.conf, then edit it and look for the lines
[formatter_logfileformatter]
format=%(levelname)s %(asctime)s %(filename)s:%(lineno)d - %(message)s
Change the 'format' line to suit your needs. There is information on the format for this here. The available attributes that can be written to the file from each log record are given here.