util/managedfile: fix symlink creation for local case

[saschahauer]

When a HTTPProvider driver is used a second time the link to the file already exists, so instead of just creating it we must replace it as done with the ln -f flag in the remote case. In the local case we currently get a FileExistsError when creating the link over an already existing one. Fix this by removing the old link before re-creating it.

Fixes: 18646f7 ("util/managedfile: replace ssh usage for local case")

Description

Checklist

• Documentation for the feature
• Tests for the feature

• The arguments and description in doc/configuration.rst have been updated

• Add a section on how to use the feature to doc/usage.rst

• Add a section on how to use the feature to doc/development.rst

• PR has been tested

• Man pages have been regenerated

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 45.9%. Comparing base (be8f3a2) to head (e057597).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
labgrid/util/managedfile.py	66.6%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #1900   +/-   ##
======================================
  Coverage    45.9%   45.9%           
======================================
  Files         180     180           
  Lines       14496   14498    +2     
======================================
+ Hits         6666    6667    +1     
- Misses       7830    7831    +1     

Flag	Coverage Δ
3.10	45.9% <66.6%> (+<0.1%)	⬆️
3.11	45.9% <66.6%> (+<0.1%)	⬆️
3.12	45.9% <66.6%> (+<0.1%)	⬆️
3.13	45.9% <66.6%> (+<0.1%)	⬆️
3.14	45.9% <66.6%> (+<0.1%)	⬆️

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