Several changes to RabbitMQ cartridge

[anefassa]

• Fixed issues which prevented multiple instances of RabbitMQ from starting in different openshift applications running on the same node. (This was mainly related to the management plugin attempting to bind to all interfaces). Change needed in rabbitmq.config.erb.install
• Fixed md5 checksum issue. Correct syntax requires double space between md5 and filename. This fix was still missing in one place and therefore would cause RabbitMQ to be downloaded everytime.
• Fixed inconsistency in variable name. BROKER_IP and BROKER_HOST were both being used and therefore the same variable name and code could not be used by scalable and non-scalable apps. Now consistent across the board.
• Expose RabbitMQ Admin Gui and api for browser access and also publish admin port for access in scalable applications. This allows for instance to have a scalable app that has a perl component (or other) monitoring Rabbit through the management plugin.
• Included app name into Rabbit nodename config. This is not technically necessary but can help Openshift administrator determine to which app a certain Rabbit process belongs to, especially when Rabbit is part of scalable app and the app name is then not part of the DNS name of the Rabbit Gear.