Small fixes for pdist (#16210)
Summary:
pdist was recently patched to remove buggy batch support and fix issues
with large tensors. This fixed missed a few spots, and didn't handle a
few recommendations that this commit addresses.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16210
Differential Revision: D13791914
Pulled By: gchanan
fbshipit-source-id: 0595841be1b298f7268fd4c02a6628acfec918f2
