Authorization.load_config breaks when authorization config contains scope based permission linked with anything other than a role based policy

[sras1599]

Its pretty clear that the library only supports loading role based policies for now. When creating a scope based permission, we should first check if the policy linked to that permission has been loaded by us and if not, we should skip adding that policy to the policies attribute of the Authorization class. Since we're pretty much doing the same thing with resource based permissions, I'm not sure why we haven't done the same with scope based permissions.