Default policies set on Client instance do not get applied

[jhecking]

Setting a default policy on a Client instance, e.g. Client#default_write_policy, Client#default_read_policy, etc., is broken since v2.0. The client specific default policies are ignored: The client either uses the policy passed into a specific request or uses a new WritePolicy, ReadPolicy, etc. instance with the default values specified in the respective policy class.