Simplify trigger files

[rtonsing]

The JSON file from Workflow is copied directly by dopull.py to ibiblio for cron-dopush processing. It would be better to use it as the trigger to puller.py, and let it pass it along.

In other words, for the JSON file:

1. dopull.py calls updatehosts.py, which creates an empty trigger file for puller.py.
2. dopull.py copies the JSON file to ibiblio, for cron-dopush.

Two scripts creating two trigger files. It would be simpler to just use the JSON file.

Also, dopull.py runs on pglaf, it makes more sense to move the action to puller.py on ibiblio, making it more localized.