Fix slow power state change

[bdraco]

We should check the result when the first future returns instead of waiting for both

[codecov-commenter]

Codecov Report

Merging #393 (cef9533) into master (c302593) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #393   +/-   ##
=======================================
  Coverage   93.80%   93.80%           
=======================================
  Files          16       16           
  Lines        3180     3180           
=======================================
  Hits         2983     2983           
  Misses        197      197           

Impacted Files	Coverage Δ
flux_led/aiodevice.py	98.94% <100.00%> (-0.01%)	:arrow_down:
flux_led/aioprotocol.py	100.00% <100.00%> (ø)