Default shuffling settings

[sylwiaszunejko]

In other drivers (Rust, java) by default replicas are shuffled. In python-driver there is an option shuffle_replicas in TokenAwarePolicy, but it is disabled by default. I think we need to change this default.

python-driver/cassandra/policies.py

Line 481 in c587c97

shuffle_replicas = False

[dkropachev]

To be done after #477