Fix log_prob() in torch.distributions.Uniform, HalfCauchy and Gamma (#23017)
Summary:
This fixes https://github.com/pytorch/pytorch/issues/22970. Specifically, `torch.distributions.uniform.Uniform.log_prob()` now works even if `value` is passed as a python float.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23017
Differential Revision: D16383258
Pulled By: vincentqb
fbshipit-source-id: 26943c33431d6da6f47e0897d6eda1c5f5541d28
