'Notify the backend that it\'s frozen.
We use set to prohibit the creation of any new resources
on the backend, or any modifications to existing items on
a backend.  We set/enforce this by not allowing scheduling
of new volumes to the specified backend, and checking at the
api for modifications to resources and failing.
In most cases the driver may not need to do anything, but
this provides a handle if they need it.
:param context: security context
:response: True|False'

def freeze_backend(self, context):

    return True
