previously in run_app_paas.sh, we captured stdout from the app and
piped that into the log file. However, this came up with a bunch of
problems, mainly:
* exceptions with stack traces often weren't formatted properly,
and kibana could not parse them
* celery logs were duplicated - we'd collect both the json logs and
the human readable stdout logs.
instead, with the updated utils library, we can use that to log json
straight to the appropriate directory directly.
