Stop double-logging the build id

There is a logging adapter that preprends the job id to log lines, so
putting it into the message as well is duplication. This should turn
this:

  2017-07-27 19:45:00,836 DEBUG zuul.AnsibleJob: [build:
68c5833049c34d4c9e564811c43ad303] Job 68c5833049c34d4c9e564811c43ad303:
git updates complete

into:

  2017-07-27 19:45:00,836 DEBUG zuul.AnsibleJob: [build:
68c5833049c34d4c9e564811c43ad303] Git updates complete

Change-Id: I5e25510d87f195f4f241a83d8faf6515232c6b4d
1 file changed