Provide constructors for Context
Provide constructors for Context

As a Task implementation is being tested a Context object has to be
mocked to pass into the init and exec methods. Context class should
provide a variety of constructors to mock the Context object.

Signed-off-by: Tommy Shiou <fd59d852321c3431be8a979962d50c7894293a47@turn.com>

turn/sorcerer