Use cheaper check in isTensorList (#33528)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/33528
Test Plan: Imported from OSS
Reviewed By: ajyu
Differential Revision: D19989166
Pulled By: zdevito
fbshipit-source-id: b0c484e037ca48226ed4d9204a06982e0c627ff0
