Add poll in confluent producer to fix BufferError

[kumaranvpl]

Description

Looks like BufferError is triggered because of lack of poll. Bug and fix for it is explained here - https://stackoverflow.com/a/62412437/3664629

Fixes #1276

Type of change

Please delete options that are not relevant.

• Documentation (typos, code examples, or any documentation updates)
• Bug fix (a non-breaking change that resolves an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a fix or feature that would disrupt existing functionality)
• This change requires a documentation update

Checklist

• My code adheres to the style guidelines of this project (scripts/lint.sh shows no errors)
• I have conducted a self-review of my own code
• I have made the necessary changes to the documentation
• My changes do not generate any new warnings
• I have added tests to validate the effectiveness of my fix or the functionality of my new feature
• Both new and existing unit tests pass successfully on my local environment by running scripts/test-cov.sh
• I have ensured that static analysis tests are passing by running scripts/static-anaylysis.sh
• I have included code examples to illustrate the modifications

[kumaranvpl]

@Lancetnik Let's merge it after getting exception stack trace from Willis in discord. This is just for confirmation. Shall I bump up the version also for this fix?

[Lancetnik]

@kumaranvpl use should bymo version, if u want to upload this fix to pypi