Daskify Earth-Sun distance correction.

[sjoro]

This PR fixes the calculation of Earth-Sun distance correction. Up to now, this correction converted the data from a dask-array to a numpy-array.

• Passes flake8 satpy

[coveralls]

Coverage increased (+0.002%) to 90.469% when pulling d030fd1 on sjoro:fix_earthsun into 5cf76e6 on pytroll:master.

[coveralls]

Coverage increased (+0.002%) to 90.469% when pulling d030fd1 on sjoro:fix_earthsun into 5cf76e6 on pytroll:master.

[codecov]

Codecov Report

Merging #1358 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1358   +/-   ##
=======================================
  Coverage   90.46%   90.46%           
=======================================
  Files         228      228           
  Lines       33211    33217    +6     
=======================================
+ Hits        30045    30051    +6     
  Misses       3166     3166           

Impacted Files	Coverage Δ
satpy/readers/utils.py	90.17% <100.00%> (+0.17%)	⬆️
satpy/tests/reader_tests/test_utils.py	100.00% <100.00%> (ø)

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