Refactors all of keystone's dependency injection to maintain a
single centralized repository of instantiated objects. This
means that we are no longer having to resolve order. All
objects that need to reference the various manager APIs simply
do so via the __getattr__ built into the Manager common object
or the ProviderAPIMixin object.
This is also the first step towards correcting our tests to
where they cannot run "load_backends" multiple times.
This forces any/all managers to properly run super()
as the way to register the api is via __init__.
This eliminates all use of the @dependency.requires and
@dependency.provides decorators, simplifying the objects
all around.
Any instantiations of a Manager after keystone is running
will now generate an error, ensuring everything for keystone
is running before handling requests. An exception is for
CLI and CLI tests, as the CLI may directly instantiate
managers and will not lock the registry.
Change-Id: I4ba17855efd797c0db9f4824936b49e4bff54b6a
81f9fe6fed