Fixes the adding of the observer to the FloatFunctional (#24418)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/24418
Fixes #24394
The observer is not added correctlty, because one of the conditions is not met.
Test Plan: Imported from OSS
Differential Revision: D16833951
Pulled By: zafartahirov
fbshipit-source-id: bb4699e6a1cf6368c7278272a68e5e7c6d3f59a8
