Adapt rabbitmq module for Fuel

* Add service_provider param
* Add config_kernel_variables, config_variables, environment_variables
  params and configure them to ensure the same rabbit config as it was
* Adjust debug log_levels for rabbit config as well
* Move custom init scripts for rabbit to nailgun module
* Remove rspecs for custom init scripts for rabbit module as obsoleted

Related blueprint merge-openstack-puppet-modules

Change-Id: I6e631b975c5835d2d6f1984d5a070a45231fe9ab
Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>