Support for Blacklisting Specific Tests in Mint

[romayalon]

We are running Mint against a custom S3-compatible backend (NooBaa) where a small number of features are intentionally unimplemented/have known issues.
Being able to skip those tests without modifying the source would improve automation and integration into our CI pipelines.
Is there a way to do so?

I saw MINT_MODE option and that you allow testing a specific sdk, but it's not exactly what i'm looking for.

Would you be open for receiving a PR that will allow selection of tests?
Thanks in advance.

[rraulinio]

@romayalon Feel free to open up a PR as such.