Treat symlinks to directories like directories

[hupfdule]

It seems that the first try (#432) was not enough. Now symlinks should be
detected in all cases.

[codecov]

Codecov Report

Merging #443 (fe9e275) into master (0587a7b) will decrease coverage by 0.00%.
The diff coverage is 20.00%.

@@            Coverage Diff             @@
##           master     #443      +/-   ##
==========================================
- Coverage   34.21%   34.20%   -0.01%     
==========================================
  Files         129      129              
  Lines        4030     4034       +4     
  Branches      539      539              
==========================================
+ Hits         1379     1380       +1     
- Misses       2521     2523       +2     
- Partials      130      131       +1     

Flag	Coverage Δ
api	33.83% <20.00%> (-0.03%)	⬇️
ui	34.49% <ø> (ø)

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Impacted Files	Coverage Δ
api/scanner/scanner_user.go	54.79% <20.00%> (-0.84%)	⬇️

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