[NOMERGE] Revert "MRG: fix bug in get_fdata return value"

[effigies]

This was the PR that #665 first showed up in. I want to see if somehow it actually caused these problems.

Reverts #638

[codecov-io]

Codecov Report

Merging #677 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #677      +/-   ##
==========================================
+ Coverage   88.86%   88.88%   +0.01%     
==========================================
  Files          93       93              
  Lines       11378    11378              
  Branches     1869     1869              
==========================================
+ Hits        10111    10113       +2     
+ Misses        930      929       -1     
+ Partials      337      336       -1

Impacted Files	Coverage Δ
nibabel/dataobj_images.py	100% <0%> (+4.44%)	⬆️

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[coveralls]

Coverage increased (+0.009%) to 91.835% when pulling b67d079 on revert-638-array-image-casting into 7877add on master.

[effigies]

Still failing, so I don't think it's #638.