Updated base image in Dockerfile and changed CMD to reference correct file

Also, fixed up environment variable to use RABBITMQ_NODE_PORT, which is
what RabbitMQ expects (http://www.rabbitmq.com/configure.html).

Implements: blueprint kube-rabbitmq-container
Change-Id: Iacc2ea5d3c4a002e6920ed17cb21733a0cbd8d21
Merge "Updated base image in Dockerfile and changed CMD to reference correct file"