Add optional extra_sasl_client_attrs to hive Connection

[baolsen]

For the Hive connection, this PR adds a simple kwargs-like parameter which is passed down to the SASL client. It intentionally will override any attributes set by PyHive, if they have the same name.

This allows customisation of SASL client properties directly if needed by an application.

We have a use case where we have to provide specific SASL client attributes to get the connection to work.

[CLAassistant]

All committers have signed the CLA.

[baolsen]

@mdeshmu , this one is ready for CI and review. Thanks

[mdeshmu]

Please test the changes and share the results. https://github.com/dropbox/PyHive#tips-for-test-environment-setup cc: @bkyryliuk