cassandra-stress has no option to force hostname validation

[dimakr]

cassandra-stress has no option to enforce hostname validation when client-to-node encryption is enabled.

We need to clarify if hostname validation is enforced by default on a system level (perhaps via a dedicated Java system property) or, if not, should it be enforced on an application level in driver.

Fixes: https://github.com/scylladb/qa-tasks/issues/1728