Reverted Erlang package to default one on Sensu branch

The official RabbitMQ package (https://www.rabbitmq.com/releases/rabbitmq-server/v2.8.4/rabbitmq-server-2.8.4-1.noarch.rpm) doesn't like erlang solution rpm so we'll revert it for now, it doesn't really matter on the Sensu branch, only for the regular Kazoo one.