This is a speculative fix as the problem is observed only on CI.
When run_async is called right after driver_connect and get_cql
it fails with ConnectionException('Host has been marked down or
removed').
If the approach proves to be succesfull we can start to deprecate
base get_cql in favor of get_ready_cql. It's better to have robust
testing helper libraries than try to take care of it in every test
case separately.
Fixes#17713Closesscylladb/scylladb#17772
With auth-v2 we can login even if quorum is lost. So test
which checks if error occurs in such situation is deleted
and the opposite test which checks if logging in works was
added.
