Fix Adagrad optimizer not working with DDP/GPU

[awaelchli]

What does this PR do?

Fixes #6824

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[codecov]

Codecov Report

Merging #7277 (a3f7f84) into master (16d6c98) will decrease coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #7277   +/-   ##
======================================
- Coverage      91%     91%   -0%     
======================================
  Files         200     200           
  Lines       12854   12941   +87     
======================================
+ Hits        11722   11776   +54     
- Misses       1132    1165   +33     

[tchaton]

LGTM !

[pep8speaks]

Hello @awaelchli! Thanks for updating this PR.

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2021-04-30 17:48:44 UTC