[fix] refactor tests and fix state_dict

[andersonic]

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• Did you write any new necessary tests?

What does this PR do?

Fixes state_dict and refactors tests further

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[codecov]

Codecov Report

Merging #45 into master will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #45      +/-   ##
==========================================
- Coverage   94.20%   94.18%   -0.02%     
==========================================
  Files          35       35              
  Lines        2071     2065       -6     
==========================================
- Hits         1951     1945       -6     
  Misses        120      120              

Flag	Coverage Δ
#Python	94.18% <100.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
fairscale/optim/adam.py	93.04% <100.00%> (-0.35%)	⬇️

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[andersonic]

8/19/2020 2:25PM NOT READY FOR REVIEW

[andersonic]

8/19/2020 3:08PM READY

[sidgoyal78]

Thanks for the refactor. Looks good to me.