Turn off scalar_checks for _th_multinomial_alias_draw. (#29946)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29946
it requires > 0-dimensional tensors.
Test Plan: Imported from OSS
Differential Revision: D18548050
Pulled By: gchanan
fbshipit-source-id: 4d1e3b53bd701137cc2cb674f95627a5e064a274
