…orp/go-azure-sdk`

* Update all instances where response structs previously referenced `*interface{}`
  for discriminated models, but now return a (non-pointer) named interface.

* Where payloads for discriminated models previously used maps as a crutch, attempt
  to use the child model type wherever possible.

* For `aurerm_role_management_policy`, the child models are currently not resolved
  correctly in Pandora and as such don't yet exist in the SDK. As a workaround,
  define a type for this model in the resource package so that it can be typed,
  and crucially so that it can satisfy the new parent model interface.

…f func

…computed values are unknown/zero at plan time

…est as it is only changing two properties and one of them is ForceNew