Scottx611x/handle admin users specially when determining ownership

[scottx611x]

get_owner() doesn't have great performance, so only use it when we have to i.e. when the requester is a superuser

[codecov]

Codecov Report

Merging #3080 into develop will decrease coverage by 0.09%.
The diff coverage is 80%.

@@            Coverage Diff             @@
##           develop    #3080     +/-   ##
==========================================
- Coverage    60.63%   60.53%   -0.1%     
==========================================
  Files          434      434             
  Lines        28074    27620    -454     
  Branches      1281     1281             
==========================================
- Hits         17022    16721    -301     
+ Misses       11052    10899    -153

Impacted Files	Coverage Δ
refinery/core/api.py	38.29% <0%> (-1.18%)	⬇️
refinery/core/test_views.py	100% <100%> (ø)	⬆️
refinery/core/views.py	47.01% <66.66%> (-7.23%)	⬇️

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[jkmarx]

Great, thanks.