Clients subclass the RestClient to allow attributes to be
overrided by each client and allow better code reuse.

Changes the RestClient to set the token and base_url when
it is needed for a request. Also allows for it to be cleared
so that it can be renewed.

Fixes lp#977594

Change-Id: I040d1c171a4018326a5b700e303652c95a3b3542
10 files changed