Fix flake on rabbitmq_mqtt auth_SUITE

[MarcialRosales]

Proposed Changes

Separate invalid client test from the valid one onto separate group and this way they use different SSL certs

Types of Changes

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• Bug fix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)
• Build system and/or CI

[ansd]

CI fails

[MarcialRosales]

This fix was only for the flake on the mqtt auth_SUITE ... I cannot see any test suite related to mqtt or mqtt's auth_SUITE failing besides the dialyzer suite.
I have noticed though that the selenium test is failing. The change done on this PR is totally unrelated. I am looking at this selenium failure now locally. I have run it two times in CI and it is failing in the same test.