* Move zuul configuration to .zuul.d directory. It allows to place job
definitions into separate files (we have a lot of jobs).
* Copy `extra` files to the right folder
* Add check for rally results directory existance before fetching it
* Stop play if `rally task start` fails with unexpected error code
* Export RALLY_PLUGINS_DIR and RALLY_EXTRA_DIR environment variables
before launching rally task, to provide backward compatibility.
(see https://github.com/openstack/mistral/blob/master/rally-jobs/task-mistral.yaml#L1 )
* Save one line message about happened error
* Load custom plugins
Change-Id: I1004afb29b9c173e414c59ef54bf58458b5d9422
859924eeb4