Fix cache folder copying in v.0.12

[greschd]

Fixes #1744 on the 0.12 branch.

[codecov-io]

Codecov Report

Merging #1746 into release_v0.12.2 will increase coverage by <.01%.
The diff coverage is 100%.

@@                 Coverage Diff                 @@
##           release_v0.12.2    #1746      +/-   ##
===================================================
+ Coverage            54.65%   54.65%   +<.01%     
===================================================
  Files                  246      246              
  Lines                32423    32421       -2     
===================================================
- Hits                 17721    17720       -1     
+ Misses               14702    14701       -1

Impacted Files	Coverage Δ
aiida/orm/implementation/sqlalchemy/node.py	68.17% <100%> (-0.08%)	⬇️
aiida/orm/implementation/django/node.py	75.83% <100%> (-0.08%)	⬇️
aiida/common/folders.py	80.23% <0%> (+0.59%)	⬆️

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