fix env variable name (pytorch#63)

Revert "[Dynamo] allow dynamic callables on tensor variables (pytorch…

…#137…" (pytorch#8)

This reverts commit 882f853f4179975aa2e98aa64dffe8e3b282013a.

Co-authored-by: Adrian Ostrowski <81568391+aostrowski-hbn@users.noreply.github.com>

Fix incorrect trace of post-accumulate grad hook on tensor with zero …

…dimensions

pytorch#135226

Change-Id: Ic23442910ebe217a14a1762a78d0195b13d80111