Cinder installation cleanup

 * Make a clear dinstinction between yum and deb commands/configs.
 * Adapt the RabbitMQ configuration to what's been used in the previous
   sections.
 * Use /etc/tgt/targets.conf as tgt config file. It is more generic and
   available on all supported distributions.
 * Rework the markup to make the source and the output a bit clearer (I
   hope).

Change-Id: Ie66c88b9c804d10600b26f6ffa478083fa55d1f6
Fixes: bug #1199951
Merge "Cinder installation cleanup"