Add additional rabbitmq parameters in rabbitmq.yaml.example

[alvin-huang]

In the Datadog integration examples, the RabbitMQ one (https://github.com/DataDog/dd-agent/blob/master/conf.d/rabbitmq.yaml.example) had some additional parameters not currently available in the Puppet module.

This PR covers a couple different changes:

1. Adds the following parameters to the RabbitMQ template:

   • ssl_verify
   • tag_families
   • nodes
   • nodes_regexes
   • queues_regexes

2. Sets defaults according to the example file:

   • username = 'guest'

   • password = 'guest'

   • ssl_verify = true

   • tag_families = false

     While these defaults are implicitly being set in the checks, I thought it would be clearer for users if they saw it in Puppet to reflect what the python scripts are doing in places like (https://github.com/DataDog/dd-agent/blob/master/checks.d/rabbitmq.py#L114-L115)
     Additionally, because these defaults are set, we don't need to check them in the erb template.

3. Add parameter validation to fail fast

[truthbk]

Thank a lot for this @alvin-huang! This looks pretty much ready at first glance, I'll take a closer look and hopefully merge soon! Thanks a bunch for updating the tests too! 🙇

[qnm]

Having the queue_regexes param would be a huge win for my team. 👍

[truthbk]

I just took a look at this and it definitely doesn't look like it'll cause any breakage for older manifests. I'm merging this, will run a few tests to decide if there's any (unlikely) tweaking necessary. Thank you very much @alvin-huang, for the PR and the detailed explanation.