[rabbitmq] Fixed #2905 - add ssl_verify option

[iancward]

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What does this PR do?

[rabbitmq] Fixes #2905 by adding ssl_verify instance config option, which can be used to skip ssl verification for API calls.

Motivation

We use a vendor app that bundles RabbitMQ using self-signed certificates, and we'd like to monitor it using Datadog.

Testing Guidelines

An overview on testing
is available in our contribution guidelines.

Additional Notes

I didn't add/change any tests for this, but I'd be willing to add some if I can get some guidance on it.

[olivielpeau]

Thanks @iancward! Changes look good, no need to add tests I think.

I've rebased your branch on top of the current master to include the CI fixes introduced by #2995

I'll merge as soon as the CI passes, thanks again!