This flag will show playbook output from non-failing commands. -v is also added to /usr/bin/ansible, but not yet used.
I also gutted some internals code dealing with 'invocations' which allowed the callback to know what module invoked
it. This is not something 0.5 does or needed, so callbacks have been simplified.
Playbook test for no vars_files with len(), but that excepts if play.vars_files==None, as can happen when there's a vars_files section with no vars files listed. What is the ansible way: ignore, warn, or fail with message (instead of traceback)?
