Fix puppet-uchiwa beaker tests

We are currently unable to run the puppet-uchiwa beaker tests for two reasons:

1. The latest version of puppetlabs/apt (1.7.0) is installed with puppetlabs/rabbitmq. However, later in the script, we attempt to install version 1.6.0. This operation generates an error.

  The solution is to install puppetlabs/apt version 1.6.0 before puppetlabs/rabbitmq, so we can install the desired version of puppetlabs/apt and satisfy the puppetlabs/rabbitmq's dependency.
1. The latest puppetlabs/rabbitmq module (v 3.4.0) is incompatible with the latest rabbitmq (v 4.1). There is currently a [PR open](https://github.com/puppetlabs/puppetlabs-rabbitmq/pull/250) in order to fix this.

  The solution is to install rabbitmq 3.3.5, which is compatible with the latest rabbitmq puppet module. Puppet won't install rabbitmq during its run. This needs cleaning up as soon as puppetlabs merges the PR and releases a compatible module.