BF: create_sibling cp -- use -R for --recursive and -p for --preserve

[yarikoptic]

So works also on OSX

could be seen among fails against released version on https://github.com/datalad/git-annex/runs/1638321268?check_suite_focus=true#step:12:2515

[codecov]

Codecov Report

Merging #5269 (0a0bd72) into maint (db77587) will increase coverage by 0.01%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##            maint    #5269      +/-   ##
==========================================
+ Coverage   90.44%   90.46%   +0.01%     
==========================================
  Files         294      294              
  Lines       40991    40991              
==========================================
+ Hits        37076    37084       +8     
+ Misses       3915     3907       -8     

Impacted Files	Coverage Δ
datalad/distribution/create_sibling.py	85.67% <66.66%> (ø)
datalad/downloaders/tests/test_http.py	90.49% <0.00%> (+1.90%)	⬆️

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[mih]

LGTM!

[kyleam]

Note to aid any future digging: gh-5108 made these same changes on master.

[yarikoptic]

damn... indeed, should have just adopted that PR changes for maint :-/