overrides the rabbitmq_plugin to include plugins_path setting

The plugins_path setting is needed for RH based systems, which have
the tools installed under <prefix>/bin and not <prefix>/sbin

32   plugins_path:
33     description:
34     | - Specify a custom path to the binaries
35     required: false
36     version_added: "1.3"
37     default: null
refactor vagrantfile and site.yml so that it works with clustered boxes
adding centos/RH and clustered rabbit support