Support multiple inheritance in torch.distributions (#16772)
Summary:
This adds calls to `super().__init__()` in three classes in torch.distributions.
This is needed when `Distribution` and `Transform` objects are used with multiple inheritance, as e.g. combined with `torch.nn.Module`s. For example
```py
class MyModule(torch.distributions.Transform, torch.nn.Module):
...
```
cc martinjankowiak esling who have wanted to use this pattern, e.g. in #16756
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16772
Differential Revision: D13978633
Pulled By: soumith
fbshipit-source-id: 8bc6cca1747cd74d32135ee2fe588bba2ea796f1
