Do not use the context parameter on refresh()

Now all RPC objects already have a context embedded within them so we
can ignore the context parameter on the refresh() method (it was the
last method using this parameter). This patch also:

* Update the Docstrings from the @remotable methods to let the user know
  that the context parameter is not being used. The @remotable decorator
  still requires that the method it's decorating have a context as it's
  first argument, but that's going to change in the future.

* All code and tests were updated to not pass the context to refresh(),
  save() and destroy() methods.

Closes-Bug: #1314732
Change-Id: Ibb338b909d99862ae048d605e66b8831d8c2128d